Health Encyclopedia

Poison ivy - oak - sumac rash

Definition

Poison ivy, oak, and sumac are plants that commonly cause an allergic skin reaction. The result is typically an itching, red rash with bumps or blisters.

Considerations

Poison ivy is one of the most frequent causes of skin rash among children and adults who spend time outdoors. The plant can be found throughout the United States, except in the Southwest, Alaska, and Hawaii. It has three shiny green leaves and a red stem. Poison ivy typically grows in the form of a vine, often along riverbanks.

Poison oak is primarily found on the West Coast. It grows in the form of a shrub and has three leaves similar to poison ivy.

Poison sumac grows abundantly along the Mississippi River. It grows as a woody shrub. Each stem contains 7-13 leaves arranged in pairs.

Causes

The rash is caused by skin contact with the oily sap (or resin) of these plants. Smoke from burning these plants can cause the same reaction. The oily resin usually enters the skin rapidly, and is seldom transferred from person to person. The rash is NOT caused by the fluid from the blisters. Thus, once the person has washed the oil off the skin, the rash is usually not contagious.

Keep in mind that the resin may last for long periods on contaminated clothing, pets, tools, shoes, and other surfaces. These contaminated items can cause future rashes long after the initial exposure.

Symptoms

A red rash and extreme itching.
The rash erupts in streaks or patches where the plant touched the skin.
The rash includes red bumps and may also form large, weeping blisters.
The reaction can vary from mild to severe. Hospitalization is sometimes required.

The rash usually appears within a couple of days after contact with the plant's oils. The worst stage is often from days 4 to 7. The rash may last for 1 to 3 weeks.

First Aid

Wash the skin thoroughly with soap and warm water. Because the resin enters skin quickly, try to wash it off within 30 minutes. A product called Tecnu, available in camping stores and some pharmacies, is very effective at removing the oils.
Scrub under the fingernails with a brush to prevent the resin from spreading to other parts of the body.
Wash clothing and shoes with soap and hot water. Resin can linger on them.
Promptly bathe animals to remove the oils from their fur.
Body heat and sweating can aggravate the itching. Stay cool and apply cool compresses to your skin.
Calamine lotion and hydrocortisone cream can be applied to the skin to reduce itching and blistering. Bathing in lukewarm water with an oatmeal bath product, available in drugstores, may soothe itchy skin. Aluminum acetate (Domeboro solution) soaks can also help to dry the rash and reduce itching.
If creams, lotions, or bathing do not stop the itching, antihistamines may be helpful.
In severe cases, especially rash around the face or genitals, your physician may prescribe oral or injected steroids.

Do Not

DO NOT touch skin or clothing that still have the resins.
DO NOT burn poison ivy, oak, or sumac to get rid of it. The resins can be spread via smoke, and can cause severe reactions in people who are far downwind.

Call immediately for emergency medical assistance if

Call 911 or go to an emergency room if:

Someone is suffering a severe allergic reaction, such as swelling or difficulty breathing, or has had a severe reaction in the past.
Someone has been exposed to the smoke of a burning plant.

Call your provider if:

Itching is severe and cannot be controlled.
The rash affects your face, lips, eyes, or genitals.
The rash shows signs of infection, such as pus, yellow fluid leaking from blisters, odor, or increased tenderness.

Prevention

Wear long sleeves, long pants, and socks when walking in areas where these plants may grow.
Skin products such as Ivy Block lotion can be applied beforehand to reduce the risk of a rash.

Other steps include:

Learn to identify poison ivy, oak, and sumac. Teach your children to identify them as soon as they are able.
Remove these plants if they grow near your home (but never burn them).
Be aware of resins carried by pets.
Wash as soon as possible after a suspected exposure.

References

Auerbach PS. Wilderness Medicine. 4^th Ed. St. Louis, MO: Mosby:2001;194-195.

Marx JA, Hockberger RS, Walls RM, eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 5^th Ed. St. Louis, MO: Mosby; 2002:1647-1648,2200.

Habif, TP. Clinical Dermatology. 4^th Ed. St. Louis, MO: Mosby;2004:25,85-89,402.

Review Date:5/15/2006
Reviewed By:Eric Perez, MD, Department of Emergency Medicine, St. Luke's-Roosevelt Hospital Center, New York, NY. Review provided by VeriMed Healthcare Network.

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