Poison Ivy and Poison Oak

Definition

Poison ivy and poison oak are plants that cause an allergic skin reaction in most people who are exposed to them.

Description

Poison ivy, which is generally thought of as a climbing vine, can also grow as a shrub or bush. It has leaves that are elliptical in shape and grow in groups of three on a stem. Poison ivy is common in the United States, except in the southwest, Alaska, and Hawaii. Poison oak, which grows as a shrub, has leaves that are shaped like oak leaves and also grow in groups of three to a stem. Poison oak is common in the United States, especially on the west coast from Mexico to Canada.

Not everyone is sensitive to poison ivy and poison oak; however, nine out of ten people who come in contact with either of the plants will have an allergic reaction to some degree. All parts of the plants are poisonous and the amount of time it takes for an allergic reaction to develop varies from person to person. The extent and severity of the reaction depends on the length of exposure, type of contact, and how sensitive the person is to the plants. If a person is going to have an allergic reaction, it will usually occur within one or two days of exposure. However, some people have a reaction within an hour, whereas others don't experience a reaction until five days after the exposure.

Causes and symptoms

The substance that causes the allergic reaction is the same for both plants. It is an oily resin called urushiol. It only takes a small amount of the resin to cause a reaction. The resin can be transferred to the skin by directly touching the plant or indirectly by coming in contact with something that has touched the plant, such as tools, animals, or clothing. Although animals are rarely affected, they can carry the resin on their fur and transfer it to humans. According to the experts at the University of Maryland Medical Center, the "chemical [resin] can remain active for more than a year."

The symptoms for poison ivy and poison oak are the same. Usually the first symptoms to appear are itchiness and swelling in the areas of contact. The itchy rash that follows is made up of small pimple-like bumps (sometimes referred to as papules), as well as blisters that later break open, ooze, and crust over.

Diagnosis

A diagnosis is made based on the symptoms and a physical examination of the patient.

In some cases, people have jobs that make it difficult for them to avoid poison ivy and poison oak, such as people who work in wooded areas or on construction sites, for example. Employees without health insurance may be covered by workers compensation.

Treatment

Anyone who comes in contact with either plant should wash the exposed area with soap and water immediately. Taking a bath immediately after contact is not recommended, because that could spread the resin to other areas of the body. All clothing, including shoes and shoelaces, should be removed carefully and either washed separately or discarded.

For minor cases, hydrocortisone cream and Calamine lotion can provide relief until the symptoms disappear. Over-the-counter Benadryl capsules help with the itching. Some people find oatmeal or baking soda baths to be soothing as well. Oral steroids, such as prednisone, are available for more serious cases, especially those affecting the face, eyes, mouth, or genitals. If signs of infection develop, such as pus and a fever, patients should contact their doctors.

Patients should consult their physicians before they use any ointments that contain benzocaine or zirconium, because they can cause an allergic reaction that worsens the condition. Antihistamine ointments are not recommended for the same reason. The experts at the Alabama Cooperative Extension System caution that "some people have severe allergic reactions to these plants and can have swelling in the throat, breathing problems, weakness, dizziness, and bluish lips." Emergency medical care should be sought if any serious reactions occur.

Prognosis

In most cases, the condition goes away in two weeks.

Prevention

The best prevention is know what the plants look like and to avoid them. A common saying should be kept in mind: Leaves of three, let them be.

People who plan to be in an area where poison ivy and poison oak might be found should wear protective clothing, such as long-sleeved shirts and long pants.

Eradication of the plants should be handled with care. As stated by the experts at the Alabama Cooperative Extension System, "burning can be dangerous and is not recommended for disposal or as a control measure, because the toxic oil from the plant can be carried in the smoke." Instead they recommend spraying the plants with glyphosate, which is commonly known as the brands Roundup or Kleenup.

Resources

OTHER

Common Pesky Plants: Poison Ivy & Poison Oak Alabama Cooperative Extension. [cited march 19, 2005]. 〈http://www.aces.edu/Tallapoosa/weed-control/poison-ivy.htm〉.

Poison Ivy University of Maryland Medical Center. [cited march 19, 2005]. 〈http://www.umm.edu/〉.