Symptoms and Complications

The effects of the contact dermatitis caused by poison ivy range from a mild, short-lived redness to severe swelling and blisters. Often, the rash contains linear streaks of tiny, itching blisters (vesicles). The rash area may be very small, or may cover a large area of the body. It rarely appears on the soles of the feet or palms of the hand. Usually, the rash first becomes noticeable as patches of red, itchy skin. Small blisters then form, filled with a clear fluid, and eventually break open. In severe reactions, the rash will develop into swollen, extremely painful areas of skin filled with fluid. Itching and a temporary thickening or scaliness of the affected skin may last for days or weeks.

Exposure to poison ivy can cause severe allergic complications, such as a more general swelling, headache, fever, or infection. A doctor should be consulted if the rash stays red and itchy for more than two weeks, or if the rash is over most of the body or near the eyes. Also, the urushiol toxin in poison ivy is not killed by fire. As a result, being exposed to or inhaling the smoke from burning poison ivy can cause a severe allergic reaction, both inside the body as well as on the skin.

Making the Diagnosis

Figuring out the cause of a case of contact dermatitis isn't always easy because the possibilities of contacts with allergens or irritants are endless. Also, many people don't remember what they've touched, or where they might have been exposed. Having said that, a poison ivy rash can usually be quickly identified if someone or their doctor is familiar with the plant's effects. One of the big hints is the distribution of the rash, which is usually in lines where the exposure to the plant occurs and then the rash is subsequently scratched.

Treatment and Prevention

Most cases of the rash can be self-treated using calamine* lotion or over-the-counter ointments and creams containing zinc oxide. Avoid using antihistamine and anesthetic (e.g., benzocaine) creams. These may be effective, but they may also cause an allergic reaction. Applying cold compresses for 15 to 30 minutes at a time several times a day will help with the itching and blistering. A baking soda paste (3 teaspoons of baking soda and 1 teaspoon of water) can be applied to the rash, and colloidal oatmeal baths (e.g., Aveeno) can also provide relief. Burow's solution can be applied as a damp compress for period of less than 20 minutes. If the previous measures do not improve the rash, then hydrocortisone cream or ointment can be applied. Corticosteroids or antihistamines taken by mouth may also relieve the symptoms, but both drugs can have unwanted side effects and should be used only on the advice of a health professional. A cortisone injection may relieve the itching, particularly within 24 hours of exposure.

Anyone with complications from a severe case, or with a rash that is not improving with self-treatment, needs to see a doctor. If the case is so severe that a more general illness (fever, nausea, dehydration) develops, a doctor may recommend injections of a corticosteroid drug.

The best way to deal with poison ivy and its relatives is to learn to recognize the plants, and then stay out of reach. If you suspect you've been in contact with a poison ivy plant, wash the affected and surrounding areas immediately and thoroughly with soap and water. Change your clothes right away. Carefully clean the skin, clothes, shoes, and tools and anything that might have picked up the plant's toxic resin. If you are going into poison ivy country, you can try one of the "barrier" lotions available from outdoor suppliers. These coat the skin in order to stop the urushiol poison from causing a reaction, as the toxin can remain on clothing for a while. Finally, the old folk tale about eating poison ivy leaves to get immunity is just a myth. Never eat the leaves or berries of wild plants. Many of them can cause dangerous reactions in humans.

*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For more information on brand names, speak with your doctor or pharmacist.