Lice infestation

Definition

A lice infestation, or pediculosis, is caused by parasites living on human skin. Lice are tiny, wingless insects with sucking mouthparts that feed on human blood and lay eggs on body hair or in clothing. Lice bites can cause intense itching .

Description

There are three related species of human lice that live on different parts of the body:

• Head lice, Pediculus humanus capitis
• Body lice, Pediculosis humanus corpus
• Pubic lice, Phthirus pubis, commonly called "crab") lice

Pediculosis capitis is an infestation of head lice. A body lice infestation is called pediculosis corporis. Pediculosis palpebrarum or Phthiriasis palpebrarum, caused by crab lice, is an infestation of the eyebrows and eyelashes.

Lice infestations are not usually dangerous. However, head lice infestations present a serious public health problem because they spread easily among schoolchildren. In general, lice infestations occur in crowded, unsanitary facilities, including prison, military, and refugee camps. Lice infestations also occur frequently among the homeless.

Lice are transmitted through personal contact or infected clothing, bedding, or towels. Pubic lice are sexually transmitted. Lice do not jump, hop, or fly and they do not live on pets.

Head lice infestations are extremely common among children in schools, childcare facilities, camps, and playgrounds. They are the second most common communicable health problem in children, after the common cold , and appear to be on the increase. Six to 12 million American children get head lice every year. In developing countries, more than 50% of the general population may be infested. Head lice can affect anyone, regardless of race, sex, socio-economic class, or personal hygiene. However children aged three to ten and their families are most affected. Girls and women are more susceptible than boys and men. Although American black children are much less likely to have head lice than white or Hispanic children, the incidence is increasing, particularly in black children with thick, kinky hair or hair extensions or wraps. In Africa, head lice have adapted their claws to the curly, elliptical hair shafts of blacks. In developing countries, head lice infestations are a significant cause of contagious bacterial infections . Neither frequent brushing nor shampooing nor hair length affects the likelihood of head lice infestation.

Head lice live and crawl on the scalp, sucking blood every three to six hours. Their claws are adapted for clinging to hair or clothing. Adult head lice can be silvery-white to reddish-brown. They are about the size of a sesame seed, about 0.6 inches (1–4 mm.) long. Female lice lay their eggs in sacs called nits that are about 0.04 inches (1 mm.) long and are glued to shafts of hair close to the scalp. During her one-month lifespan, a female louse may lay more than 100 eggs. The nymphs hatch in three to 14 days and must feed on blood within one day. Nymphs are smaller and lighter in color than adults and become sexually mature after 9 to 12 days. Head lice cannot survive without a human host for more than a few days at most.

Body lice lay their nits in clothing or bedding. Occasionally the nits are attached to body hair. Body lice nits are oval and yellow to white in color. They may not hatch for up to 30 days. Nymphs mature in about 7 days. Body lice can live without human contact for up to 10 days.

Body lice infestations are usually associated with poor personal hygiene, as may occur during war or natural disasters or in cold climates. Body lice can carry and transmit disease-causing organisms, including those for epidemic typhus, relapsing fever , and trench fever. Trench fever is self-limiting. However, typhus and relapsing fever have mortality rates of five to 10 percent. The elderly are most vulnerable to these diseases.

Pubic lice can survive for one to two weeks without human contact and occasionally are transmitted through infected bedding, towels, or clothing. Pubic lice have large front legs and look like tiny crabs. Females are larger than males. Nits hatch in about one week and the nymphs mature in about seven days. Although pubic lice do not carry diseases, they often are found in association with other sexually transmitted diseases.

Causes & symptoms

Lice are endemic in human populations, spreading by personal contact or contact with infested clothing or other personal items. Lice also can be transmitted when unaffected clothing is stored with infested items. Among children, head lice are commonly transmitted by the sharing of hats, combs, brushes, hair accessories, headphones, pillows, and stuffed toys.

Lice infestations are characterized by intense itching caused by an allergic reaction to a toxin in the lice saliva. The itching can interfere with sleep and concentration. Repeated bites can lead to generalized skin eruptions or inflammation. Scratching or scraping at the bites can cause hives or abrasions that may lead to bacterial skin infections. Swelling or inflammation of the neck glands are common complications of head lice.

Body lice bites first appear as small red pimples or puncture marks and may cause a generalized skin rash. Intense itching can result in deep scratches around the shoulders, flanks, or neck. If the infestation is not treated, complications may develop, including headache , fever, and skin infection with scarring. Crab lice in children may be an indication of sexual activity or abuse.

Diagnosis

Lice usually are diagnosed by the itching. However, itching may not occur until several weeks after infestation, if at all. The tickling caused by moving lice may be noticeable. Definite diagnosis requires identification of lice or their nits.

Head lice may cause irritability in children. Scalp irritations or sores may be present. Although head lice in children are usually limited to the scalp, in adults, head lice can spread to eyebrows, eyelashes, mustaches, and beards. An adult louse may be visible as movement on the scalp, especially around the ears, nape of the neck, and center line of the crown—the warmest parts of the head. Since less than 20 mature lice may be present at a given time during infestation, the nits often are easier to spot. Nits vary in color from grayish-white to yellow, brown, or black. They are visible at the base or on the shaft of individual hairs. Applying about 10 ounces (280 grams) of isopropyl (rubbing) alcohol to the hair and rubbing with a white towel for about 30 seconds releases lice onto the towel for identification.

Body lice appear similar to head lice, however they burrow into the skin and are rarely seen except on clothing, where they lay their nits in seams. Over time, body lice infestations can lead to a thickening and discoloring of the skin around the waist, groin, and upper thighs. Scratching may cause sores that become infected with bacteria or fungi.

Pubic lice usually appear first on genital hair, although they may spread to other body hair. In young children, pubic lice are usually seen on the eyebrows or eyelashes. Pubic lice appear as brown or gray moving dots on the skin. There are usually only a few live lice present and they move very quickly away from light. Their white nits can be seen on hair shafts close to the skin. Although pubic lice sometimes produce small, bluish spots called maculae ceruleae on the trunk or thighs, usually it is easier to spot scratching marks. Small, dark-brown specks of lice excretion may be visible on underwear.

Since pediculicides (medications for treating lice) are usually strong insecticides with potential side effects, it is important to rule out other causes of scratching and skin inflammation. The oval-shaped head lice nits can be distinguished from dandruff because they are glued at an angle to the hair shaft. In contrast, flat, irregularly

shaped flakes of dandruff shake off easily. A healthcare professional needs to distinguish between body lice and scabies—a disease caused by skin mites—and between pubic lice and eczema , a skin condition.

Treatment

Most treatments apply to all types of lice infestation and, particularly with head lice, treatments are an area of great controversy. The questionable safety and effectiveness of allopathic (fighting disease with remedies that produce effects different from those produced by the disease) treatments has spurred the search for alternative therapies. With any type of treatment, itching may not subside for several days.

Head lice

Most authorities believe that head lice should be treated immediately upon discovery. Before beginning any treatment:

• Test a small scalp section for allergic reactions to the medication
• A vinegar rinse helps loosen nits
• Wash hair with regular shampoo

Treatments for applying to the scalp and hair include:

• Olive oil or petroleum ointment to smother the lice. Cover the head with a shower cap, four to six hours per day for three to four days
• Olive oil (three parts) and essential oil of lavender (one part)
• Herbal shampoos or pomades
• A mixture of paw paw, thymol, and tea tree oil
• A combination of coconut oil, anise , and ylang ylang
• Other mixtures of essential oils
• RID Pure Alternative, a nontoxic, hypoallergenic, dye and fragrance-free product
• A spray containing phenethyl propionate, cedar oil, peppermint oil, and sodium lauryl sulfate (LiceFreee)
• Cocamide DEA (a lathering agent), triethanolamine (a local irritant), and disodium EDTA (a chelator), (SafeTek) is both a nontoxic pediculicide and a conditioner for combing out lice and nits

Cutting the hair or shaving the head may be effective. Aromatherapies also are available. Infested eyelashes and eyebrows should be treated with petroleum jelly for several days and the nits should be plucked off with tweezers or fingernails.

Body lice

Treatment for body lice is a thorough washing of the entire body and replacing infected clothing. Clothing and bedding should be washed at 140°F (60°C) and dried at high temperature, or dry-cleaned.

Pubic lice

A common herbal treatment for pubic lice consists of:

• Oil of pennyroyal (Mentha pulegium), 25%
• Oil of garlic (Allium sativum), 25%
• Distilled water, 50%

The mixture is applied to the pubic hair once a day for three days. Anyone with pubic lice should be tested for other sexually transmitted diseases.

Nit Removal

Neither alternative nor allopathic treatments will kill all lice nits. Hair and pubic lice nits must be removed manually to prevent re-infestation as the eggs hatch. Manual removal alone may effectively treat a lice infestation.

Before removing nits, one of the following procedures may be used:

• 50% vinegar rinse to loosen the nits
• wiping individual locks of hair from base to tip with a cloth soaked in vinegar
• 8% formic acid solution applied to the hair for 10 minutes, rinsed out, and towel-dried
• catching live lice with a comb, tweezers, fingernails, or by sticking them with double-sided tape
• enzymatic lice-egg remover

Furthermore:

• Hair should be clean, damp, and untangled
• Hair conditioner should not be used on hair treated allopathically
• Remove clothing and place a towel between the hair and shoulders
• Divide hair into square-inch (six sq.-cm.) sections. Clips or elastics can be used to divide long hair

Nits are manually removed with:

• Any fine-toothed comb, including pet flea combs
• A specialized nit comb (LiceMeister, LiceOut)
• A battery-powered vibrating or anti-static comb
• Tweezers
• Baby safety scissors
• Fingernails

To comb out nits:

• Comb along each hair section from scalp to tip
• Between each passing, dip the comb in water and wipe with a paper towel to remove lice and nits
• Hold the comb to the light to be sure it is clean
• If necessary, clean comb with a tooth or fingernail brush or dental floss
• Work under a good light, with a magnifying glass if necessary
• Do not rush. Long, thick hair may take an hour to comb out thoroughly
• Wash towels and clothing after combing
• Repeat at least twice a week for at least two weeks

Re-infestation

Re-infestation occurs often with all types of lice dueto:

• Ineffective or incomplete treatment
• Chemical-resistant lice
• Failure to remove live nits
• Failure to treat all infected household members, playmates, or partners
• Failure to remove nits from clothing, bedding, towels, or other items
• Re-infestation from another source

Re-infestation with body or pubic lice can be prevented by washing underclothes, sleepwear, bedding, and towels in hot, soapy water and drying with high heat for at least 20 minutes. Clothing infected with body lice should be ironed under high heat. Sexual partners should be treated for public lice simultaneously and should reexamine themselves for several days.

To prevent head lice re-infestation:

• Repeat lice checks and nit removal daily until none are found
• Notify school, camp, or daycare, and parents of playmates
• Check and if necessary treat household members, playmates, schoolmates, school or daycare staff, and others in close contact with an infestation
• Treat combs and brushes with rubbing alcohol, Lysol, or soapy water above 130°F (54°C)
• Wash all bedding, clothing, headgear, scarves, and coats with soapy water at 130°F (54°C) and dry with high heat for at least 20 minutes
• Wash or vacuum stuffed animals and other toys
• Vacuum all helmets, carpets, rugs, mattresses, pillows, upholstery, and car seats
• Remove the vacuum cleaner bag after use, seal in a plastic bag, and place in the outside garbage
• Non-washable items should be dry cleaned or sealed in a plastic bag for up to four weeks
• Lice pesticide sprays for inanimate objects are toxic and are not recommended
• Repeat treatment if necessary

Allopathic treatment

All types of lice are treated allopathically with insecticidal lotions, shampoos, or cream rinses. However, experts disagree about the effectiveness and/or safety of pediculicides. Pediculicides do not kill nits, so nit removal and a second application in seven to 10 days may be necessary. Pediculicides can be poisonous if used improperly or too frequently and overuse can lead to the proliferation of chemically resistant lice. The residue may remain on the hair for several weeks and can cause skin or eye irritations.

Pediculicides should not be used:

• Near broken skin, eyes, or mucous membranes
• In the bathtub or shower
• By pregnant or nursing women or children under two
• By those with allergies, asthma, epilepsy , or some other medical conditions

Pyrethroids

All U.S. Food and Drug Administration (FDA)-approved non-prescription pediculicides contain relatively safe and effective pyrethroids. Insecticidal pyrethrins (0.33%) (RID, A-200) are extracts from chrysanthemum flowers. Permethrin (1%)(Nix) is a more stable synthetic pyrethrin. Pyrethroid pediculicides usually also contain 4% piperonyl butoxide.

To treat with pyrethroids:

• Apply for specified time, usually 10 minutes.
• Thoroughly rinse out.
• Do not wash hair for one or two days after treatment.
• Do not use cream rinse, hair spray, mousse, gels, mayonnaise, or vinegar before or within one week after treatment. These products may reduce pediculicide effectiveness

During the 1990s, as schools began requiring children to be lice and nit-free, the use of pyrethroids rose significantly and the FDA began receiving reports of ineffectiveness. The FDA ordered new labeling of pyrethroid pediculicides on the outside of the carton, in simpler language, and with more information, to take effect in 2005–2006. Permethrin sprays for treating mattresses, furniture, and other items are not recommended.

Other insecticides

Prescription insecticides are used when other lice treatments fail or cannot be used. These pesticides include:

• Malathion (0.5% in Ovide), a neurotoxic organophosphate, was withdrawn from the U.S. market due to an increase in malathion-resistant lice and re-introduced in 1999. It is foul-smelling and flammable. Sometimes infested clothing is treated with a 1% malathion powder
• Lindane (1% or higher) (Kwell), an organochloride neurotoxin, can induce seizures and death in susceptible people, even when used according to the directions. In 2003 the FDA required new labeling and a reduction in bottle size
• Ivermectin (Stromectol), an oral treatment for intestinal parasites, is effective against head lice but has not been approved for that use by the FDA

Infested eyelashes are treated with a thick coating of prescription petroleum ointment, applied twice daily for ten days.

Prognosis

Despite the presence of chemically resistant lice and the thoroughness required to prevent re-infestation, essentially all lice infestations can be eradicated eventually.

Prevention

Prevention of lice infestation depends on adequate personal hygiene and the following public health measures:

• Avoid sharing combs, brushes, hair accessories, hats, towels, or bedding
• Check hair and scalp weekly for lice and nits
• Limit sexual partners

Regular lice checks in schools and "no nit" re-entry policies have not been shown to be effective. The American Academy of Pediatrics, the Harvard School of Public Health, and the National Association of School Nurses recommend their elimination, although many healthcare professionals disagree.

Scientists have identified both the gene that enables head and body lice to digest blood and the gene that helps lice combat deadly infections, with the potential for new treatments and preventions for lice infestation.

Resources

BOOKS

Goldberg, Burton, et al. "Children's Health." Alternative Medicine: The Definitive Guide. 2nd ed. Berkeley, CA: Ten Speed Press, 2002.

Grossman, Leigh B. Infection Control in the Child Care Center and Preschool. Philadelphia: Lippincott Williams & Wilson, 2003.

PERIODICALS

Blenkinsopp, Alison. "Head Lice." Primary Health Care 13 (October 2003): 33–34.

Burgess, I. F. "Human Lice and Their Control." Annual Review of Entomology 49 (2004): 457.

Elston, D. M. "Drug-Resistant Lice." Archives of Dermatology. 139 (2003): 1061–1064.

Evans, Jeff "Pediatric Dermatology: Simple Methods Often Best: Lice, Mosquitoes, Warts." Family Practice News. 34 (January 15, 2004): 56.

Flinders, David C., and Peter De Schweinitz. "Pediculosis and Scabies." American Family Physician 69 (January 15, 2004): 341–352.

Heukelbach, Jorg, and Hermann Feldmeier. "Ectoparasites—The Underestimated Realm." Lancet 363 (March 13, 2004): 889–891.

Hunter, J. A., and S. C. Barker. "Susceptibility of Head Lice (Pediculus humanus capitis ) to Pediculicides in Australia." Parasitology Research 90 (August 2003): 476–478.

Kittler, R., et al. "Molecular Evolution of Pediculus humanus and the Origin of Clothing." Current Biology 13 (August 19, 2003): 1414–1417.

"Recommendations Provided for Back-to-School Head Lice Problem." Health & Medicine Week October 6, 2003: 329.

Yoon, K. S., et al. "Permethrin-Resistant Human Head Lice, Pediculus capitis, and Their Treatment." Archives of Dermatology 139 (August 2003): 1061–1064.

Zepf, Bill. "Treatment of Head Lice: Therapeutic Options." American Family Physician 69 (February 1, 2004): 655.

OTHER

Lice. MayoClinic.com. August 5, 2002 [cited April 18, 2004].<http://www.mayoclinic.com/invoke.cfm?id=DS00368>.

Lindane Shampoo and Lindane Lotion Questions and Answers. Center for Drug Evaluation and Research, U.S. Food and Drug Administration. April 15, 2003 [cited April 18, 2004].<http://www.fda.gov/cder/drug/infopage/lindane/lindaneQA.htm>.

ORGANIZATIONS

American Academy of Dermatology (AAD). P.O. Box 4014, Schaumburg, IL 60168-4014. 847-330-0230. <http://www.aad.org>.

American Academy of Pediatrics (AAP). 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. 847-434-4000. [email protected] <http://www.aap.org>.

Centers for Disease Control and Prevention, National Center for Infectious Diseases, Division of Parasitic Diseases. 1600 Clifton Road, Atlanta, GA 30333. 404-639-3534. 800-311-3435. <http://www.cdc.gov/ncidod/dpd/parasites/lice/default.htm>.

National Pediculosis Association (NPA), Inc. 50 Kearney Road, Needham, MA 02494. 781-449-NITS. [email protected]. <http://www.headlice.org>.

Rebecca J. Frey, PhD

Margaret Alic, PhD

Lice infestation

Definition

A lice infestation, or pediculosis, is caused by parasites living on human skin. Lice are tiny, wingless insects with sucking mouthparts that feed on human blood and lay eggs on body hair or in clothing. Lice bites can cause intense itching .

Description

There are three related species of human lice:

• head lice, Pediculus humanus capitis
• body lice, Pediculosis humanus corpus
• pubic lice, Phthirus pubis, commonly called crab lice

Pediculosis capitis is an infestation of head lice. A body lice infestation is called pediculosis corporis. Pediculosis palpebrarum or phthiriasis palpebrarum, caused by crab lice, is an infestation of the pubic hair.

Head lice live and crawl on the scalp, sucking blood every three to six hours. Their claws are adapted for clinging to hair or clothing. Adult head lice can be silvery-white to reddish-brown. They are about the size of a sesame seed. Female lice lay their eggs in sacs called nits that are about 0.04 in (1 mm) long and are glued to shafts of hair close to the scalp. During her one-month lifespan a female louse may lay more than 100 eggs. The nymphs hatch in three to 14 days and must feed on blood within one day. Nymphs are smaller and lighter in color than adults and become sexually mature after nine to 12 days.

Body lice lay their nits in clothing or bedding. Occasionally the nits are attached to body hair. Body lice nits are oval and yellow to white in color. They may not hatch for up to 30 days. Nymphs mature in about seven days.

Pubic lice have large front legs and look like tiny crabs. Females are larger than males. Nits hatch in about one week and the nymphs mature in about seven days.

Transmission

Lice are endemic in human populations, spreading through personal contact or contact with infested clothing or other personal items. They can be transmitted when unaffected clothing is stored with infested items. Among children head lice are commonly transmitted by the sharing of hats, combs, brushes, hair accessories, headphones, pillows, and stuffed toys . Pubic lice are sexually transmitted, although occasionally they can be transmitted through infested bedding, towels, or clothing.

Lice do not jump, hop, or fly and they do not live on pets. Head lice cannot survive without a human host for more than a few days at most. Body lice can live without human contact for up to 10 days. Pubic lice can survive for one to two weeks without human contact.

Demographics

Head lice infestations are extremely common among children in schools, childcare facilities, camps, and playgrounds. They are the second most common communicable health problem in children, after the common cold , and appear to be on the increase. Some 6 to 12 million American children get head lice every year. In developing countries more than 50 percent of the general population may be infested. Although anyone can get head lice, children aged three to ten and their families are most affected. Girls and women are more susceptible than boys and men. Although American black children are much less likely to have head lice than white or Hispanic children, the incidence is increasing, particularly in black children with thick hair, hair extensions, or wraps. In Africa head lice have adapted their claws to the curly, elliptical hair shafts of blacks. Neither frequent brushing or shampooing nor hair length affects the likelihood of a head lice infestation.

In general body lice infestations occur in crowded, unsanitary facilities, such as prisons and military or refugee camps. They usually are associated with poor personal hygiene, as may occur during war or natural disasters or in cold climates. They are common among the homeless.

Causes and symptoms

Lice infestations are characterized by intense itching caused by an allergic reaction to a toxin in lice saliva. The itching can interfere with sleep and concentration. Repeated bites can lead to generalized skin eruptions or inflammation. Swelling or inflammation of the neck glands are common complications of head lice.

Body lice bites first appear as small red pimples or puncture marks and may cause a generalized skin rash. Intense itching can result in deep scratches around the shoulders, flanks, or neck. If the infestation is not treated, complications may develop, including headache , fever , and skin infection with scarring.

When to call the doctor

A doctor may need to distinguish between body lice and scabies (a disease caused by skin mites) and between pubic lice and eczema (a skin condition). A doctor should be consulted if complications develop from a lice infestation or if a child contracts a bacterial infection from scratching the bites.

Diagnosis

Lice usually are diagnosed by the itching; however, itching may not occur until several weeks after infestation, if at all. The tickling caused by moving lice may be noticeable. Definite diagnosis requires identification of lice or their nits.

Head lice may cause irritability in children and scalp irritations or sores may be present. Head lice in children are usually confined to the scalp. An adult louse may be visible as movement on the scalp, especially around the ears, nape of the neck, and centerline of the crown, the warmest parts of the head. Since less than 20 mature lice may be present at a given time during infestation, the nits often are easier to spot. Nits vary in color from grayish-white to yellow, brown, or black. They are visible at the base or on the shaft of individual hairs. Applying about 10 oz (280 gm) of isopropyl (rubbing) alcohol to the hair and rubbing with a white towel for about 30 seconds releases lice onto the towel for identification.

Body lice appear similar to head lice; however, they burrow into the skin and are rarely seen except on clothing where they lay their nits in seams. Over time body lice infestations can lead to a thickening and discoloring of the skin around the waist, groin, and upper thighs.

Pubic lice usually appear first on genital hair, although they may spread to other body hair. In young children pubic lice usually are seen on the eyebrows or eyelashes. Pubic lice appear as brown or gray moving dots on the skin. There are usually only a few live lice present and they move very quickly away from light. Their white nits can be seen on hair shafts close to the skin. Although pubic lice sometimes produce small, bluish spots called maculae ceruleae on the trunk or thighs, usually it is easier to spot scratching marks. Small, dark-brown specks of lice excretion may be visible on underwear.

Since pediculicides (medications for treating lice) are usually strong insecticides with potential side effects, it is important to rule out other causes of scratching and skin inflammation. Oval-shaped head lice nits can be distinguished from dandruff because they are glued at an angle to the hair shaft, whereas flat, irregularly shaped flakes of dandruff shake off easily.

Treatment

Most authorities believe that head lice should be treated immediately upon discovery. Before beginning any treatment, parents should test a small scalp section for allergic reactions to the medication, use a vinegar rinse to help loosen nits, and wash hair with regular shampoo.

Infested eyebrows should be treated with petroleum jelly for several days and the nits should be plucked off with tweezers or fingernails. Infested eyelashes are treated with a thick coating of prescription petroleum ointment, applied twice daily for ten days.

The treatment for body lice is a thorough washing of the entire body and replacement of infected clothing. Clothing and bedding should be washed at 140°F (60°C) and dried at high temperature or dry-cleaned.

Pediculicides

Head and pubic lice infestations usually are treated with insecticidal lotions, shampoos, or cream rinses. These pediculicides should not be used on children under two; near broken skin, eyes, or mucous membranes; in the bathtub or shower; by those with allergies , asthma , epilepsy, or certain other medical conditions. Itching may not subside for several days following treatment.

All U.S. Food and Drug Administration (FDA)approved non-prescription pediculicides contain relatively safe and effective pyrethroids. Insecticidal pyrethrins (0.33%) (RID, A-200) are extracts from chrysanthemum flowers. Permethrin (1%)(Nix) is a more stable synthetic pyrethrin. Pyrethroid pediculicides also usually contain 4 percent piperonyl butoxide.

Pyrethroids are applied for a specified length of time (usually ten minutes) and then thoroughly rinsed out. The hair should not be washed for one or two days after treatment. Cream rinse, conditioner, hair spray, mousse, gel, mayonnaise, or vinegar should not be used before treatment or within one week after treatment since these products can reduce pediculicide effectiveness.

Prescription insecticides are used when other lice treatments fail or cannot be used. The following are prescription insecticides, which carry certain risks:

• Malathion (0.5% in Ovide), a neurotoxic organophosphate, was withdrawn from the U.S. market due to an increase in malathion-resistant lice. It was reintroduced in 1999. It is foul-smelling and flammable. Sometimes infested clothing is treated with a 1 percent malathion powder.
• Lindane (1% or higher) (Kwell), an organochloride neurotoxin, can induce seizures and death in susceptible people, even when used according to the directions. In 2003 the FDA required new labeling and a reduction in bottle size.
• Ivermectin (Stromectol), an oral treatment for intestinal parasites, is effective against head lice but as of 2004 had not been approved for that use by the FDA.

Experts disagree about the effectiveness and/or safety of pediculicides. Pediculicides do not kill nits, so nit removal and a second application in seven to 10 days are required. During the 1990s, as schools began requiring children to be lice- and nit-free, the use of pyrethroids rose significantly and the FDA began receiving reports of their ineffectiveness. Pediculicides can be poisonous if used improperly or too frequently and overuse can lead to the proliferation of chemically resistant lice. Pediculicide residue may remain on the hair for several weeks and can cause skin or eye irritations.

Alternative treatment

Olive oil or petroleum ointment may be used to smother head lice. After applying to the hair and scalp, the child's head is covered with a shower cap for four to six hours. The treatment is repeated daily for three or four days. Cutting the hair or shaving the head also may be effective. Other treatments for head lice include:

• olive oil (three parts) and essential oil of lavender (one part)
• herbal shampoos or pomades
• RID Pure Alternative, a nontoxic, hypoallergenic, dye- and fragrance-free product
• a spray containing phenethyl propionate, cedar oil, peppermint oil, and sodium lauryl sulfate (LiceFree)
• cocamide DEA (a lathering agent), triethanolamine (a local irritant), and disodium EDTA (a chelator) (SafeTek) are both a nontoxic pediculicide and a conditioner for combing out lice and nits.

A common herbal treatment for pubic lice consists of pennyroyal oil (25%), garlic oil (25%), distilled water (50%). The mixture is applied to the pubic hair once a day for three days.

Nit removal

Treatment does not kill all lice nits. Hair and pubic lice nits must be removed manually to prevent re-infestation as the eggs hatch. Manual removal alone may treat a lice infestation effectively.

Before removing head lice nits, one of the following procedures may be used:

• a 50 percent vinegar rinse to loosen the nits
• wiping individual locks of hair from base to tip with a cloth soaked in vinegar
• catching live lice with a comb, tweezers, fingernails, or by sticking them with double-sided tape
• an enzymatic lice-egg remover

In addition, hair should be clean, damp, and untangled; clothing should be removed and a towel placed between the hair and shoulders; the hair should be divided into square-inch sections with the use of clips or elastics to divide long hair.

Head lice nits are removed by combing through each hair section from scalp to tip. Between each passing, the comb should be dipped in water and wiped with a paper towel to remove lice and nits. The comb should be held up to the light to be sure it is clean. If necessary the comb may be cleaned with a toothbrush, fingernail brush, or dental floss. Good light and possibly a magnifying glass are required. Long, thick hair may take an hour to comb out thoroughly. Towels and clothing should be washed after combing. The process should be repeated at least twice a week for at least two weeks.

Nits also can be manually removed with any fine-toothed comb, including pet flea combs, a specialized nit comb (LiceMeister, LiceOut), a battery-powered vibrating or anti-static comb, tweezers, baby safety scissors, and fingernails.

Re-infestation

Re-infestation occurs often with all types of lice due to the following:

• ineffective or incomplete treatment
• chemical-resistant lice
• failure to remove live nits
• failure to treat all infected household members and playmates
• failure to remove nits from clothing, bedding, towels, or other items
• re-infestation from another source

Head lice re-infestation can be prevented by the following:

• repeating lice checks and nit removal daily until no more are found
• notifying school, camp, or daycare, and parents of playmates
• checking and treating household members, playmates, schoolmates, school or daycare staff, and others in close contact with the child
• treating combs and brushes with rubbing alcohol, Lysol, or soapy water above 130°F (54°C)
• washing all bedding, clothing, headgear, scarves, and coats with soapy water at 130°F (54°C) and drying with high heat for at least 20 minutes
• washing or vacuuming stuffed animals and other toys
• vacuuming all helmets, carpets, rugs, mattresses, pillows, upholstery, and car seats (Permethrin sprays for treating mattresses, furniture, and other items are not recommended.)
• removing the vacuum-cleaner bag after use, sealing in a plastic bag, and placing in the outside garbage
• dry-cleaning non-washable items or sealing them in a plastic bag for up to four weeks
• repeating treatment if necessary

Re-infestation with body or pubic lice can be prevented by washing underclothes, sleepwear, bedding, and towels in hot, soapy water and drying with high heat for at least 20 minutes. Clothing infected with body lice should be ironed under high heat.

Prognosis

Lice infestations are not usually dangerous. Despite the presence of chemically-resistant lice and the thoroughness required to prevent re-infestation, all lice infestations are eradicated eventually.

Prevention

Prevention of lice infestation depends on adequate personal hygiene and consistently not sharing combs, brushes, hair accessories, hats, towels, or bedding. Hair should be checked weekly for lice and nits.

Regular lice checks in schools and "no nit" reentry policies have not been shown to be effective. The American Academy of Pediatrics, the Harvard School of Public Health, and the National Association of School Nurses recommend their elimination, although many healthcare professionals disagree.

Parental concerns

Usually children are not allowed to return to daycare or school until they are lice- and nit-free. The discovery of head lice may cause distress for children and their families. Parents should stay calm and explain to the child:

• what head lice are and how they are transmitted
• that lice are very common and that many—if not most—children have them at some point
• that it is nothing to be embarrassed or ashamed about
• that the infestation is not the child's fault

Scratching or scraping at lice bites may cause hives or abrasions that can lead to bacterial skin infections. In developing countries head lice infestations are a significant cause of contagious bacterial infections. Body lice can carry and transmit disease-causing organisms. Although pubic lice do not carry diseases, they often are found in association with other sexually transmitted diseases . Crab lice in children may be an indication of sexual activity or abuse.

KEY TERMS

Crabs —An informal or slang term for pubic lice.

Endemic —Natural to or characteristic of a particular place, population, or climate.

Insecticide —Any substance used to kill insects.

Lindane —A benzene compound that is used to kill body and pubic lice. Lindane is absorbed into the louse's central nervous system, causing seizures and death.

Malathion —An insecticide that can be used in 1% powdered form to disinfect the clothes of patients with body lice.

Neurotoxin —A poison that acts directly on the central nervous system.

Nits —The eggs produced by head or pubic lice, usually grayish white in color and visible at the base of hair shafts.

Pediculicide —Any substance that kills lice.

Pediculosis —A lice infestation.

Permethrin —A medication used to rid the scalp of head lice. Permethrin works by paralyzing the lice, so that they cannot feed within the 24 hours after hatching required for survival.

Petroleum jelly or ointment —Petrolatum, a gelatinous substance obtained from oil that is used as a protective dressing.

Piperonyl butoxide —A liquid organic compound that enhances the activity of insecticides.

Pyrethrin, pyrethroid —A naturally occurring insecticide extracted from chrysanthemum flowers. It paralyzes lice so that they cannot feed.

Resources

BOOKS

Derkazarian, Susan. You Have Head Lice! Danbury, CT: Scholastic Library Publishing, 2005.

Grossman, Leigh B. Infection Control in the Child Care Center and Preschool. Philadelphia: Lippincott Williams & Wilson, 2003.

Official Patient's Sourcebook on Head Lice Infestation. San Diego, CA: Icon Group International, 2002.

PERIODICALS

Blenkinsopp, Alison. "Head Lice." Primary Health Care 13 (October 2003): 33–4.

Burgess, I. F. "Human Lice and Their Control." Annual Review of Entomology 49 (2004): 457.

Elston, D. M. "Drug-Resistant Lice." Archives of Dermatology 139 (2003): 1061–4.

Evans, Jeff. "Pediatric Dermatology: Simple Methods Often Best: Lice, Mosquitoes, Warts." Family Practice News 34 (January 15, 2004): 56.

Flinders, David C., and Peter De Schweinitz. "Pediculosis and Scabies." American Family Physician 69 (January 15, 2004): 341–52.

Heukelbach, Jorg, and Hermann Feldmeier. "Ectoparasites—The Underestimated Realm." Lancet 363 (March 13, 2004): 889–91.

Kittler, R., et al. "Molecular Evolution of Pediculus humanus and the Origin of Clothing." Current Biology 13 (August 19, 2003): 1414–17.

"Recommendations Provided for Back-to-School Head Lice Problem." Health & Medicine Week (October 6, 2003): 329.

Yoon, K. S., et al. "Permethrin-Resistant Human Head Lice Pediculus capitis, and Their Treatment." Archives of Dermatology 139 (August 2003): 994–1000.

Zepf, Bill. "Treatment of Head Lice: Therapeutic Options." American Family Physician 69 (February 1, 2004): 655.

ORGANIZATIONS

American Academy of Dermatology (AAD). PO Box 4014, Schaumburg, IL 60168-4014. Web site: <www.aad.org>.

American Academy of Pediatrics (AAP). 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. Web site: <www.aap.org>.

Centers for Disease Control and Prevention. National Center for Infectious Diseases, Division of Parasitic Diseases. 1600 Clifton Road, Atlanta, GA 30333. Web site: <www.cdc.gov/ncidod/dpd/parasites/lice/default.htm>.

National Pediculosis Association (NPA), Inc. 50 Kearney Road, Needham, MA 02494. Web site: <www.headlice.org>.

WEB SITES

"Lice." MayoClinic.com, August 5, 2002 Available online at <www.mayoclinic.com/invoke.cfm?id=DS00368> (accessed December 29, 2004).

"Lindane Shampoo and Lindane Lotion Questions and Answers." Center for Drug Evaluation and Research, U.S. Food and Drug Administration, April 15, 2003. Available online at <www.fda.gov/cder/drug/infopage/lindane/lindaneQA.htm> (accessed December 29, 2004).

Rebecca J. Frey, PhD

Margaret Alic, PhD

Lice Infestation

Definition

Lice infestations (pediculoses) are infections of the skin, hair, or genital region caused by lice living directly on the body or in hats or other garments. Lice are small wingless insect-like parasites with sucking mouthparts that feed on human blood and lay their eggs on body hairs or in clothing. The name pediculosis comes from the Latin word for louse (singular) or lice (plural). Some anthropologists believe that the different species of head and body lice developed in response to humans' invention and use of clothing about 50,000 years ago.

Description

Lice infestations are not dangerous infections by themselves. It is, however a serious public health problem because some lice can carry organisms that cause other diseases, including relapsing fever, trench fever, and epidemic typhus. Although trench fever is self-limiting, the other two diseases have mortality rates of 5%-10%. Pubic lice are often associated with other sexually transmitted diseases (STDs) but do not spread them.

Lice infestations are frequent occurrences in areas of overcrowding or inadequate facilities for bathing and laundry. They are often associated with homelessness in the general population or with military, refugee, or prisoner camps in war-torn areas. All humans are equally susceptible to louse infestation; the elderly, however, are more vulnerable to typhus and other diseases carried by lice.

Causes and symptoms

The symptoms of lice infestations vary somewhat according to body location, although all are characterized by intense itching, usually with injury to the skin caused by scratching or scraping. The itching is an allergic reaction to a toxin in the saliva of the lice. Repeated bites can lead to a generalized skin eruption or inflammation.

Head lice

This type of infestation is caused by Pediculosis humanus capitis, the head louse. Head lice can be transmitted from one person to another by the sharing of hats, combs, or hair brushes. Epidemics of head lice are common among school-age children from all class backgrounds in all parts of the United States. The head louse is about 1/16 of an inch in length. The adult form may be visible on the patient's scalp, especially around the ears; or its grayish-white nits (eggs) may be visible at the base of the hairs close to the scalp. It takes between three and 14 days for the nits to hatch. After the nits hatch, the louse must feed on blood within a day or die.

Head lice can spread from the scalp to the eyebrows, eyelashes, and beard in adults, although they are more often limited to the scalp in children. The itching may be intense, and may be followed by bacterial infection of skin that has been scratched open. Another common complication is swelling or inflammation of the neck glands. Head lice do not spread typhus or other systemic diseases.

Body lice

Infestations of body lice are caused by Pediculosis humanus corporis, an organism that is similar in size to head lice. Body lice, however, are rarely seen on the skin itself because they come to the skin only to feed. They should be looked for in the seams of the patient's clothing. This type of infestation is associated by wearing the same clothing for long periods of time without laundering, as may happen in wartime or in cold climates; or with poor personal hygiene. It can be spread by close personal contact or shared bedding.

Patients with body lice often have intense itching with deep scratches around the upper shoulders, flanks, or neck. The bites first appear as small red pimples but may cause a generalized skin rash. If the infestation is not treated, the patient may develop complications that include headache, fever, and bacterial infection with scarring. Body lice can spread systemic typhus or other infections.

Pubic lice

Pubic lice are sometimes called "crabs." This type of infestation is caused by Phthirus pubis and is commonly spread by intimate contact. People can also get pubic lice from using the bedding, towels, or clothes of an infected person.

Pubic lice usually appear first on pubic hair, but may spread to other parts of the body, particularly if the patient is very hairy. Pubic lice are also sometimes seen on the eyelashes of children born to infected mothers. It is usually easier for the doctor to see marks from the patient's scratching than the bites from the lice, but pubic lice sometimes produce small bluish spots called maculae ceruleae on the patient's trunk or thighs. Pubic lice also sometimes leave small dark brown specks from their own excreted matter on the parts of the patient's underwear that cover the anal or genital areas.

Diagnosis

Doctors can diagnose lice infestations from looking closely at the parts of the body where the patient has been scratching. Lice are large enough to be easily seen with the naked eye or a magnifying glass. The eggs of pubic lice as well as head lice can often be found by looking at the base of the patient's hairs. Pediatricians are most likely to diagnose lice in school-age children.

It is important for doctors to rule out other diseases that can cause scratching and skin inflammation because the medications used to kill lice are very strong and can have bothersome side effects. The doctor will need to distinguish between head lice and dandruff; between body lice and scabies (a disease caused by skin mites); and between pubic lice and eczema. Blood tests or other laboratory tests are not useful in diagnosing lice infestations.

Treatment

Cases of head lice are usually treated with sham-poos or rinses containing either lindane (Kwell) or permethrin (Nix). Permethrin is considered preferable, however, because lindane is absorbed through the skin and may produce symptoms of neurotoxicity. The person applying the treatment should wear rubber gloves and rinse the patient's hair or body completely after use. Following the treatment, nits should be removed from the hair with a fine-toothed comb or tweezers. Lindane is also effective for treating infestations of body or pubic lice, but it should not be used by pregnant women. In most cases one treatment is sufficient, but the medication can be reapplied a week later if living lice have reappeared.

Another drug that appears to be effective in treating lice is ivermectin (Stromectol), a strong antiparasite drug that is usually given to treat intestinal worms. Two doses of the drug, however, cured 99% of cases of head lice as well as intestinal worms in a poor population with high rates of infestation with both types of parasites.

Infestations of body lice can also be treated by washing the patient's clothes or bedding in boiling water, ironing seams with an iron on a high setting, or treating the clothes with 1% malathion powder or 10% DDT powder.

If the patient's eyelashes have been infested, the only safe treatments are either a thick coating of petroleum jelly (Vaseline) applied twice daily for eight days, or 1% yellow oxide of mercury applied four times a day for two weeks. Any remaining nits should be removed with tweezers.

Patients with pubic lice should be examined and tested for other STDs.

Alternative treatment

For pubic lice, some practitioners of holistic medicine recommend a mixture of 25% oil of pennyroyal (Mentha pulegium ), 25% garlic (Allium sativum ) oil, and 50% distilled water applied three times in a three-day period, followed by removal of dormant eggs to prevent reinfestation.

Another alternative treatment for head lice is tea tree oil, sometimes called melaleuca oil. Tea tree oil appears to work well in treating head lice that have developed resistance to other preparations.

Prognosis

Lice can be successfully eradicated in almost all cases, although a growing number of cases of drug-resistant lice have been reported. As of 2004, some researchers are concerned about the rapid but unpredictable spread of these resistant lice. Ovide, a newer medication containing malathion, appears to be effective in treating patients with permethrin-resistant lice.

In general, patients are more at risk from typhus, trench fever, rickettsial infections, and other diseases spread by lice than from the lice themselves.

Prevention

There are no vaccines or skin treatments that will protect a person against lice prior to contact. In addition, lice infestation does not provide immunity against reinfection; recurrences are in fact quite common. Prevention depends on adequate personal hygiene at the individual level and the following public health measures:

• Teaching school-age children the basics of good personal hygiene, including the importance of not lending or borrowing combs, brushes, or hats.
• Notifying and treating an adult patient's close personal and sexual contacts.
• Examining homeless people, elderly patients incapable of self-care, and other high-risk individuals prior to hospital admission for signs of louse infestation. This measure is necessary to protect other hospitalized people from the spread of lice.

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD., editors. "Pediculosis." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

PERIODICALS

Downs, A. M. "Managing Head Lice in an Era of Increasing Resistance to Insecticides." American Journal of Clinical Dermatology 5 (March 2004): 169-177.

Foucault, C., D. Raoult, and P. Brouqui. "Randomized Open Trial of Gentamicin and Doxycycline for Eradication of Bartonella quintana from Blood in Patients with Chronic Bacteremia." Antimicrobial Agents and Chemotherapy 47 (July 2003): 2204-2207.

Heukelbach, J., and H. Feldmeier. "Ectoparasites—The Underestimated Realm." Lancet 363 (March 13, 2004): 889-891.

Heukelbach, J., T. Wilcke, B. Winter, et al. "Efficacy of Ivermectin in a Patient Population Concomitantly Infected with Intestinal Helminths and Ectoparasites." Arzneimittelforschung 54 (2004): 416-421.

Hunter, J. A., and S. C. Barker. "Susceptibility of Head Lice (Pediculus humanus capitis ) to Pediculicides in Australia." Parasitology Research 90 (August 2003): 476-478.

Kittler, R., M. Kayser, and M. Stoneking. "Molecular Evolution of Pediculus humanus and the Origin of Clothing." Current Biology 13 (August 19, 2003): 1414-1417.

Mills, C., B. J. Cleary, J. F. Gilmer, and J. J. Walsh. "Inhibition of Acetylcholinesterase by Tea Tree Oil." Journal of Pharmacy and Pharmacology 56 (March 2004): 375-379.

Yoon, K. S., J. R. Gao, S. H. Lee, et al. "Permethrin-Resistant Human Head Lice, Pediculus capitis, and Their Treatment." Archives of Dermatology 139 (August 2003): 1061-1064.

ORGANIZATIONS

American Academy of Dermatology (AAD). 930 East Woodfield Road, Schaumburg, IL 60173. (847) 330-0230. 〈http://www.aad.org〉.

KEY TERMS

Crabs— An informal or slang term for pubic lice.

Lindane— A benzene compound that is used to kill body and pubic lice. Lindane works by being absorbed into the louse's central nervous system, causing seizures and death.

Maculae ceruleae— Bluish or blue-grey skin eruptions often seen on the trunk or thighs of patients with pubic lice. The Latin words mean blue spots.

Malathion— An insecticide that can be used in 1% powdered form to disinfect the clothes of patients with body lice.

Nits— The eggs produced by head or pubic lice, usually grayish-white in color and visible at the base of hair shafts.

Pediculosis (plural, pediculoses)— The medical term for infestation with lice.

Permethrin— A medication used to rid the scalp of head lice. Permethrin works by paralyzing the lice, so that they cannot feed after hatching within the 24 hours required for survival.

Lice infestation

Definition

Lice infestations (pediculoses) are infections of the skin, hair, or genital region caused by lice living directly on the body or in hats or other garments. Lice are small wingless insect-like parasites with sucking mouthparts that feed on human blood and lay their eggs on body hairs or in clothing. The name pediculosis comes from the Latin word for louse (singular) or lice (plural). Some anthropologists believe that the different species of head and body lice developed in response to humans' invention and use of clothing about 50,000 years ago.

Description

Lice infestations are not dangerous infections by themselves. It is, however a serious public health problem because some lice can carry organisms that cause other diseases, including relapsing fever, trench fever, and epidemic typhus. Although trench fever is self-limiting, the other two diseases have mortality rates of 5%–10%. Pubic lice are often associated with other sexually transmitted diseases (STDs) but do not spread them.

Lice infestations are frequent occurrences in areas of overcrowding or inadequate facilities for bathing and laundry. They are often associated with homelessness in the general population or with military, refugee, or prisoner camps in war-torn areas. All humans are equally susceptible to louse infestation; the elderly, however, are more vulnerable to typhus and other diseases carried by lice.

Causes and symptoms

The symptoms of lice infestations vary somewhat according to body location, although all are characterized by intense itching , usually with injury to the skin caused by scratching or scraping. The itching is an allergic reaction to a toxin in the saliva of the lice. Repeated bites can lead to a generalized skin eruption or inflammation.

Head lice

This type of infestation is caused by Pediculosis humanus capitis, the head louse. Head lice can be transmitted from one person to another by the sharing of hats, combs, or hair brushes. The head louse is about 1/16 of an inch in length. The adult form may be visible on the patient's scalp, especially around the ears; or its grayish-white nits (eggs) may be visible at the base of the hairs close to the scalp. It takes between three and 14 days for the nits to hatch. After the nits hatch, the louse must feed on blood within a day or die.

Head lice can spread from the scalp to the eyebrows, eyelashes, and beard in adults. The itching may be intense, and may be followed by bacterial infection of skin that has been scratched open. Another common complication is swelling or inflammation of the neck glands. Head lice do not spread typhus or other systemic diseases.

Body lice

Infestations of body lice are caused by Pediculosis humanus corporis, an organism that is similar in size to head lice. Body lice, however, are rarely seen on the skin itself because they come to the skin only to feed. They should be looked for in the seams of the patient's clothing. This type of infestation is associated by wearing the same clothing for long periods of time without laundering, as may happen in wartime or in cold climates; or with poor personal hygiene . It can be spread by close personal contact or shared bedding.

Patients with body lice often have intense itching with deep scratches around the upper shoulders, flanks, or neck. The bites first appear as small red pimples but may cause a generalized skin rash. If the infestation is not treated, the patient may develop complications that include headache, fever, and bacterial infection with scarring. Body lice can spread systemic typhus or other infections.

Pubic lice

Pubic lice are sometimes called “crabs.” This type of infestation is caused by Phthirus pubis and is commonly spread by intimate contact. People can also get pubic lice from using the bedding, towels, or clothes of an infected person.

Pubic lice usually appear first on pubic hair, but may spread to other parts of the body, particularly if the patient is very hairy. It is usually easier for the doctor to see marks from the patient's scratching than the bites from the lice, but pubic lice sometimes produce small bluish spots called maculae ceruleae on the patient's trunk or thighs. Pubic lice also sometimes leave small dark brown specks from their own excreted matter on the parts of the patient's underwear that cover the anal or genital areas.

Diagnosis

Doctors can diagnose lice infestations from looking closely at the parts of the body where the patient has been scratching. Lice are large enough to be easily seen with the naked eye or a magnifying glass. The eggs of pubic lice as well as head lice can often be found by looking at the base of the patient's hairs. Pediatricians are most likely to diagnose lice in school-age children.

It is important for doctors to rule out other diseases that can cause scratching and skin inflammation because the medications used to kill lice are very strong and can have bothersome side effects. The doctor will need to distinguish between head lice and dandruff; between body lice and scabies (a disease caused by skin mites); and between pubic lice and eczema. Blood tests or other laboratory tests are not useful in diagnosing lice infestations.

Treatment

Cases of head lice are usually treated with shampoos or rinses containing either lindane (Kwell) or permethrin (Nix). Permethrin is considered preferable, however, because lindane is absorbed through the skin and may produce symptoms of neurotoxicity. The person applying the treatment should wear rubber gloves and rinse the patient's hair or body completely after use. Following the treatment, nits should be removed from the hair with a fine-toothed comb or tweezers. Lindane is also effective for treating infestations of body or pubic lice, but it should not be used by pregnant women. In most cases one treatment is sufficient, but the medication can be reapplied a week later if living lice have reappeared.

Another drug that appears to be effective in treating lice is ivermectin (Stromectol), a strong antiparasite drug that is usually given to treat intestinal worms. Two doses of the drug, however, cured 99% of cases of head lice as well as intestinal worms in a poor population with high rates of infestation with both types of parasites.

Infestations of body lice can also be treated by washing the patient's clothes or bedding in boiling water, ironing seams with an iron on a high setting, or treating the clothes with 1% malathion powder or 10% DDT powder.

If the patient's eyelashes have been infested, the only safe treatments are either a thick coating of petroleum jelly (Vaseline) applied twice daily for eight days, or 1% yellow oxide of mercury applied four times a day for two weeks. Any remaining nits should be removed with tweezers.

Patients with pubic lice should be examined and tested for other STDs.

Alternative treatment

For pubic lice, some practitioners of holistic medicine recommend a mixture of 25% oil of pennyroyal (Mentha pulegium), 25% garlic (Allium sativum) oil, and 50% distilled water applied three times in a three-day period, followed by removal of dormant eggs to prevent reinfestation.

Another alternative treatment for head lice is tea tree oil, sometimes called melaleuca oil. Tea tree oil appears to work well in treating head lice that have developed resistance to other preparations.

Prognosis

Lice can be successfully eradicated in almost all cases, although a growing number of cases of drug-resistant lice have been reported. As of 2004, some researchers are concerned about the rapid but unpredictable spread of these resistant lice. Ovide, a newer medication containing malathion, appears to be effective in treating patients with permethrin-resistant lice.

KEY TERMS

Crabs —An informal or slang term for pubic lice.

Lindane —A benzene compound that is used to kill body and pubic lice. Lindane works by being absorbed into the louse's central nervous system, causing seizures and death.

Maculae ceruleae —Bluish or blue-grey skin eruptions often seen on the trunk or thighs of patients with pubic lice. The Latin words mean blue spots.

Malathion —An insecticide that can be used in 1% powdered form to disinfect the clothes of patients with body lice.

Pediculosis (plural, pediculoses) —The medical term for infestation with lice.

Permethrin —A medication used to rid the scalp of head lice. Permethrin works by paralyzing the lice, so that they cannot feed after hatching within the 24 hours required for survival.

In general, patients are more at risk from typhus, trench fever, rickettsial infections, and other diseases spread by lice than from the lice themselves.

Prevention

There are no vaccines or skin treatments that will protect a person against lice prior to contact. In addition, lice infestation does not provide immunity against reinfection; recurrences are in fact quite common. Prevention depends on adequate personal hygiene at the individual level and the following public health measures:

• Teaching school-age children the basics of good personal hygiene, including the importance of not lending or borrowing combs, brushes, or hats.
• Notifying and treating an adult patient's close personal and sexual contacts.
• Examining homeless people, elderly patients incapable of self-care, and other high-risk individuals prior to hospital admission for signs of louse infestation. This measure is necessary to protect other hospitalized people from the spread of lice.

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD., editors. “Pediculosis.” In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

PERIODICALS

Downs, A. M. “Managing Head Lice in an Era of Increasing Resistance to Insecticides.” American Journal of Clinical Dermatology 5 (March 2004): 169–177.

Foucault, C., D. Raoult, and P. Brouqui. “Randomized Open Trial of Gentamicin and Doxycycline for Eradication of Bartonella quintana from Blood in Patients with Chronic Bacteremia.” Antimicrobial Agents and Chemotherapy 47 (July 2003): 2204–2207.

Heukelbach, J., and H. Feldmeier. “Ectoparasites—The Underestimated Realm.” Lancet 363 (March 13, 2004):889–891.

Heukelbach, J., T. Wilcke, B. Winter, et al. “Efficacy of Ivermectin in a Patient Population Concomitantly Infected with Intestinal Helminths and Ectoparasites.” Arzneimittelforschung 54 (2004): 416–421.

Hunter, J. A., and S. C. Barker. “Susceptibility of Head Lice (Pediculus humanus capitis) to Pediculicides inAustralia.” Parasitology Research 90 (August 2003): 476–478.

Kittler, R., M. Kayser, and M. Stoneking. “Molecular Evolution of Pediculus humanus and the Origin of Clothing.” Current Biology 13 (August 19, 2003):1414–1417.

Mills, C., B. J. Cleary, J. F. Gilmer, and J. J. Walsh. “Inhibition of Acetylcholinesterase by Tea Tree Oil.”Journal of Pharmacy and Pharmacology 56 (March 2004): 375–379.

Yoon, K. S., J. R. Gao, S. H. Lee, et al. “Permethrin-Resistant Human Head Lice, Pediculus capitis, and Their Treatment.” Archives of Dermatology 139 (August 2003): 1061–1064.

ORGANIZATIONS

American Academy of Dermatology (AAD). 930 East Woodfield Road, Schaumburg, IL 60173. (847) 330-0230. http://www.aad.org.

Rebecca J. Frey Ph.D.

Lice

A Lousy Deal

What Are Lice?

Who Gets Lice, and How?

What Are the Symptoms?

How Are Lice Treated?

What Else Can Be Done?

How Can Head Lice Be Prevented?

Resources

Lice are tiny insects that can be found on the scalp, body, pubic area, or clothing and whose bites may lead to severe itching.

KEYWORDS

for searching the Internet and other reference sources

Parasites

Pediculosis

Sexually transmitted diseases

A Lousy Deal

Lice are tiny insects that are found on the hairy parts of the body or in clothing. A single one of these insects is known as a louse, and the eggs of a louse are known as nits. The bites of these insects can cause severe itching. Judging from the way people talk, lice are not too popular. When people have an awful day, they say it was lousy. When they make a mess of things, they say they have loused up. When they are overly critical, they are said to be nit-picking.

What Are Lice?

The medical term for having lice is pediculosis (pe-dik-yoo-LO-sis). Lice are parasites* (PAIR-a-sites) that feed on human blood. There are three types of lice that live on humans:

* parasites

are organisms that live on other organisms and usually cause harm or disease.

• Head lice (Pediculus humanus capitus). These lice are usually found on the scalp.
• Body lice (Pediculus humanus corporis). These lice are found in clothing, from which they travel to the skin to feed.
• Pubic (PYOO-bik) lice (Phthirus pubis). These lice, also known as crab lice, are found in the pubic area, surrounding the genitals.

Who Gets Lice, and How?

Lice are a very common problem. Anyone can get lice, which are easily spread from person to person. Head lice are spread by close contact with a person who already has them. They also can be passed by sharing combs, brushes, hats, barrettes, pillows, headphones, and the like. Head lice are especially common in young children and their families. They may spread quickly among children in school or camp. They are not a sign of dirtiness or poor hygiene. Body lice usually are passed along on clothing and bedding. They are sometimes found in people who live in crowded conditions where clothes are not changed or washed very often. Pubic lice usually are spread by close physical contact involving the genital area, such as sexual contact, so typically they are found in people who are sexually active. In a few cases, they may be picked up from bedding or clothing.

What Are the Symptoms?

Head lice do not cause serious medical problems. However, they can be very annoying. The first sign of trouble usually is severe itching on the part of the body where the lice are biting. However, it may take as long as 2 or 3 weeks for the itching to start. Although it may be hard, a person with lice should try not to scratch, because this can spread the lice to other parts of the body. It also can lead to infection if germs are allowed to get into sores caused by scratching. Another possible sign of lice is a tickling feeling of something moving in the hair.

Although lice are tiny, they can be seen with the naked eye if a person looks closely. The nits, or eggs, are tiny yellow or white ovals attached to the hair near the scalp. They can be confused with dandruff or drops of hair spray. Nits take about a week to hatch into baby lice, known as nymphs. These babies turn into adults in another 7 days or so. Adult lice have six legs and are about the size of a sesame seed. They can live for up to 30 days on a person.

Head lice usually are found on the scalp. Often they are seen at the back of the neck and around the ears. In a few cases, head lice are found on the eyelashes or eyebrows. Body lice are hard to see on the body, because they burrow into the skin. They are usually easiest to see in the seams of clothing, from which they travel to the skin to feed. Pubic lice are found on the skin and hair of the pubic area. This is the area where hair grows around the genitals.

How Are Lice Treated?

Lice usually can be identified by sight. If the lice themselves are not seen, finding nits close to the scalp shows that a person has lice. The treatment for lice involves using a shampoo, cream rinse, or lotion that contains a medicine that kills lice. Such medicines are known as pediculicides (pe-DIK-yoo-li-sides). Some are sold over the counter, but others are sold only with a doctor’s prescription. Home remedies that do not include a lice-killing medicine may not always work.

When using a lice-killing medicine, read the label and follow the instructions carefully. These medicines may be harmful if not used correctly and should be used with adult supervision, as follows:

• Remove all clothing before the treatment.
• Apply the product according to instructions.
• Do not use a regular cream rinse or combination shampoo-conditioner first.
• Do not wash the hair again for a couple of days.
• Put on clean clothing after the treatment.

Special combs are sold to help remove any leftover nits from the hair. The lice-killing medicine may need to be used again in 7 to 10 days to make sure that no nits have survived. If the treatment does not work, talk to a doctor. Do not use extra amounts of medicine or more treatments than suggested.

What Else Can Be Done?

These steps must be followed along with the use of lice-killing shampoos, rinses or creams to help prevent the spread of lice to others:

• Machine wash in hot water all clothing and bedding that the person with lice touched during the 2 days before treatment.
• Then put the clothes and bedding in a dryer on the hot cycle for at least 20 minutes.
• Dry clean any clothes that cannot be washed.
• Store any clothing, bedding, or stuffed animals that cannot be washed or dry cleaned in a sealed plastic bag for at least 2 weeks.
• Soak combs and brushes for about an hour in rubbing alcohol or Lysol, or wash them in soap and hot water.
• Vacuum the floors and furniture.
• Let the school know about the lice. Stay home until 24 hours after treatment, or as long as the school requires.
• Check other people who have had close contact with a person with lice for signs that they may have caught lice, too.
• In the case of a person with pubic lice, any sex partners from the month before treatment should be treated as well.

How Can Head Lice Be Prevented?

These steps can help prevent the spread of head lice:

• Never share combs and brushes.
• Always bring your own sleeping bag and pillow to a sleep-over.
• Do not try on a friend’s hat or headphones.
• If your head itches, tell an adult right away; do not wait.

See also

Parasitic Diseases

Sexually Transmitted Diseases

Resources

Fact Sheets

National Center for Infectious Diseases. “Head Lice Infestation” and “Treating Head Lice.” To order, contact the Centers for Disease Control and Prevention, NCID, 1600 Clifton Road, N.E., Atlanta, GA 30333, (888) 232-3228. http://www.cdc.gov/ncidod

National Institute of Allergy and Infectious Diseases. “Other Important STDs.” To order, contact the NIAID Office of Communications and Public Liaison, 31 Center Drive, Building 31, Room 7A50, Bethesda, MD 20892-2520, (301) 496-5717. http://www.niaid.nih.gov

Organization

National Pediculosis Association, P.O. Box 610189, Newton, MA 02461, (781) 449-NITS. A group concerned with head lice. http://www.headlice.org