Poison Ivy (cont.)

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Is a rash from poison ivy, oak, and sumac dermatitis contagious?

The rash from poison ivy, oak, or sumac is not contagious. It cannot be spread to other parts of the body or to other people. However, if you still have traces of the plant oil (urushiol) on your hands after exposure, you can spread it to other people and to other parts of your body. Sometimes, the rash will take longer to appear in some areas of the body than in others, giving the appearance that the reaction has spread elsewhere in the body. However, only contact with the sap oil urushiol can spread the reaction, and the rash itself does not contain urushiol.

What are risk factors for poison ivy, oak, and sumac dermatitis?

Risk factors include being in outdoor areas where the plants may be present. These plants are present throughout the U.S., except for desert areas, higher elevations (above 4,000 feet), Alaska, and Hawaii. It has been estimated that about 75% of people have some degree of sensitivity to urushiol, but the degree of sensitivity varies among individuals.

How is the dermatitis of poison ivy, oak, or sumac diagnosed?

The diagnosis is generally established upon observation of the typical rash in an area that could have been exposed to the plants, along with a history of potential exposure (such as weeding a garden or walking in the woods). No special tests are required for the diagnosis. In some cases, skin inflammation due to other causes (including allergic contact dermatitis or chemical irritation) may be mistaken for poison ivy, oak, or sumac since the rash may be similar.

What is the treatment for poison ivy, oak, and sumac dermatitis?

The best approach to poison ivy, oak, or sumac dermatitis is prevention. Washing with soap and water can help reduce the severity of the rash, but this is often impractical because it has to be done at once after exposure. (After 10 minutes, only 50% of the resin is removable, and by 30 minutes only 10%.)

Most plant poison dermatitis is a mild rash that clears within five to 12 days, almost always cleared by 14-21 days. Treatment is directed at controlling the itching. Oral antihistamines, such as diphenhydramine (Benadryl), may help the itch somewhat, but often they do no more than make people drowsy. Cortisone creams, whether over the counter or by prescription, are only helpful if applied right away, before blisters appear, or much later, when the blisters have dried up. Compresses with Burow's solution (available without prescription) can help dry the ooze faster. Local anesthetic agents such as calamine lotion have also been shown to bring relief for some people. Oatmeal baths and cool compresses have also been recommended to help relieve symptoms.

When the rash is severe, such as when it affects the face or causes extensive blistering, oral steroids (for example, prednisone) can help produce rapid improvement. This course of therapy should be maintained, often in decreasing doses, for 10-14 days or even longer in some cases, to prevent having the rash rebound and become severe again. Patients who are given a six-day pack of cortisone pills often get worse again when they complete it because the dose was too low and administered for too short a time.

Folklore, medical and otherwise, endorses many other agents, including aloe leaves, vinegar, baking soda, tea bags, and meat tenderizer as treatments for poison ivy and related plant poisonings. Though these remedies are generally harmless, they are of questionable value.

Medically Reviewed by a Doctor on 9/17/2012


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