Poison Ivy, Oak, Or Sumac: Topic Overview

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Topic Overview

What are poison ivy, oak, and sumac?

Poison ivy, poison oak, and poison sumac are plants that can cause a skin rash called allergic contact dermatitis upon contact. The red, uncomfortable, and itchy rash often shows up in lines or streaks and is marked by fluid-filled bumps (blisters) or large raised areas (hives). It is the most common skin problem caused by contact with plants (plant dermatitis).

See an illustration of poison ivy, oak, and sumac leaves .

What causes a poison ivy, oak, or sumac rash?

The rash is caused by contact with an oil (urushiol) found in poison ivy, oak, or sumac. Urushiol is an allergen, so the rash is actually an allergic reaction to the oil in these plants. Indirect contact with urushiol can also cause the rash. This may happen when you touch clothing, pet fur, sporting gear, gardening tools, or other objects that have come in contact with one of these plants.

What are the symptoms of the rash?

The usual symptoms of the rash are:

Itchy skin where you came in contact with the plant.
Red streaks or lines where the plant brushed against the skin, or general redness.
Small bumps or larger raised areas (hives).
Blisters filled with fluid that sometimes leaks out.

The rash usually appears 8 to 48 hours after your contact with the urushiol. The rash will continue to develop in new areas over several days but only on the parts of your skin that had contact with the urushiol or those parts where the urushiol was spread by touching.

The rash is not contagious. You cannot catch or spread a rash once it appears, even if you touch it or the blister fluid, because the urushiol will already be absorbed or washed off the skin. The rash may seem to be spreading, but either it is still developing from earlier contact or you have touched something that still has urushiol on it.

The more urushiol you come in contact with, the more severe your skin reaction. Severe reactions to smaller amounts of urushiol also may develop in people who are highly sensitive to urushiol. Serious symptoms may include:

Swelling (edema) of the face, mouth, neck, genitals, or eyelids, sometimes to the point of being unable to open eyes.
Widespread, large blisters that ooze large amounts of fluid.

How is the rash diagnosed?

The rash usually is diagnosed during a physical examination. Your health professional will examine the rash and ask questions to find out when you were exposed to the plant and how long it took the rash to develop. If you are not sure whether you were exposed to a plant, he or she will ask about your outdoor activities, work, and hobbies.

How is the rash treated?

Most poison ivy, oak, or sumac rashes can be treated successfully at home. Initial treatment consists of washing the area with water immediately after contact with the plants. To relieve symptoms, use wet compresses and take cool baths. Nonprescription antihistamines and calamine lotion also may help relieve symptoms. Moderate or severe cases of the rash may require treatment by a health professional, who may prescribe corticosteroid pills, creams, or ointments.

How can I prevent the rash from poison ivy, oak, and sumac?

The best way to prevent the rash is to learn to identify and avoid the plants. When contact with the plants is unavoidable, heavy clothing (long pants, long-sleeved shirt, and vinyl gloves) and barrier creams or lotions may provide some protection.

Frequently Asked Questions

Learning about poison ivy, oak, and sumac:	What are poison ivy, oak, and sumac? What causes a poison ivy, oak, or sumac rash? Can I prevent the poison ivy, oak, or sumac rash? What are the symptoms of a poison ivy, oak, or sumac rash? What happens in a poison ivy, oak, or sumac rash? What increases my risk for getting a poison ivy, oak, or sumac rash? Where are poison ivy, oak, and sumac found, and what do they look like? Can other plants cause a rash? What other types of rash may look like poison ivy, oak, or sumac rash? Who is affected by poison ivy, oak, and sumac rashes?
Being diagnosed:	Who can diagnose a poison ivy, oak, or sumac rash? How is a poison ivy, oak, or sumac rash diagnosed?
Getting treatment:	How is a poison ivy, oak, or sumac rash treated? What medications will I need to take?
Living with poison ivy, oak, and sumac rash:	What can I do at home to relieve symptoms of a poison ivy, oak, or sumac rash? How often will I need to see my health professional? When should I call my health professional?

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Last updated:	January 12, 2006
Author:	Colleen Cronin
Reviewed By:	Patrice Burgess, MD - Family Medicine, H. Michael O'Connor, MD - Emergency Medicine
Editors:	Susan Van Houten, RN, BSN, MBA, Tracy Landauer

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