According to the American Academy of Dermatology, approximately 85 percent of the population will develop an allergic reaction if exposed to poison ivy, oak or sumac. The cause for the rash, blisters, and infamous itch is urushiol (pronounced yoo-Roo-shee-all), a chemical in the sap of these plants. Avoiding direct contact with the plants reduces the risk but doesn’t guarantee against a reaction. Urushiol can stick to pets, garden tools, balls, or anything it comes in contact with. If the urushiol isn’t washed off those objects or animals, just touching them–for example, picking up a ball or petting a dog–could cause a reaction in a susceptible person. The rash can often be recognized by its characteristic streaks of red blisters that are intensely itchy. The timing of the development of the rash and its severity depends to a large degree on the amount of urushiol that contacts the skin.

If you’ve been exposed to poison ivy, oak or sumac, the following measures will greatly decrease the chances of developing a rash:

1. If you are outside, but have access to water, thoroughly rinse the exposed areas of skin.
2. As soon as possible, take a regular shower with soap and warm water. Although unproven scientifically, some people claim additional benefits from the use of a “poison ivy wash” such a Zanfel.
3. Clothes, shoes, tools, and anything else that may have been in contact with urushiol should be wiped off or washed. Be sure to wear gloves or otherwise cover your hands while doing this and then discard the hand covers.

If you don’t cleanse quickly enough, or your skin is so sensitive that cleansing didn’t help, redness and swelling will appear in about 12 to 48 hours. Since oozing blisters don’t contain urushiol, the blister fluid is not capable of spreading the rash to another site on the body or to someone else. The rash, blisters and itch normally disappear in 14 to 20 days without any treatment, but few can handle the itch without some relief.

For mild cases, wet compresses or soaking in cool water may be effective. Oral antihistamines, such as Benadryl can also relieve itching. Other, over-the-counter treatments that are safe and effective for temporary relief of itching associated with poison ivy include applying calamine lotion, taking oatmeal baths, and applying a topical corticosteroid cream (Cortaid, Cortizone 10, others). For severe reactions, particularly if the rash involves the face or skin around the eyes, medical attention should be sought for treatment with oral or injected corticosteroids.

It is important to avoid scratching the rash since this could lead to the development of an infection. Also use of topical creams or sprays that contain antihistamines (e.g. Benadryl) or topical anesthetics (e.g. Lanacaine) can result in sensitization and the development of an allergic rash unrelated to the poison ivy.

There are two primary ways of avoiding the development of poison ivy rash. The best preventive measure is avoidance of exposure to the plant. Remember the saying “leaves of 3, leave it be”. Those who are highly sensitive to urushiol should learn to identify poison ivy, oak and sumac in order to avoid the itchy consequences of exposure. It’s important to know that all parts of the plant, not just the leaves, are capable of producing the allergic reaction. Also, burning the plant can release urushiol into the air creating a risk for an allergic reaction in the airways or exposed skin. The second method involves protecting the skin against exposure. Although no longer on the market, IvyBlock, a lotion containing the chemical bentoquatam, was FDA approved for absorbing urushiol and reducing the likelihood of skin reaction. A second barrier method is to wear long pants, long sleeves, boots, and gloves when exposure cannot be avoided.

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