July-September, 2003

Ask the Pharmacist
By Carrie Lee, Pharm.D., and Gene Schoonmaker, M.D.

Poison Ivy & Poison Oak: tips for preventing and treating the rashes

Summer and fall invite outdoor activities such as hiking, biking, campfires, and chopping wood. These activities increase the risk of exposure to poison ivy and poison oak. Below are tips for preventing poison ivy rash and treatment if the rash appears.

How can I prevent a poison ivy rash?

Poison oak and poison ivy are native to Missouri and Arkansas. These plants produce an oily resin (urushiol) that is released when the plant is damaged. Urushiol is the primary cause of the allergic reaction and rash seen with poison ivy or poison oak exposure. Touching a damaged plant transfers the oil onto the skin.  Burning the plant can transfer the oil into the air.

Initial exposure usually occurs on the hands, arms, and legs. Other body sites are affected when a person touches that area with hands that have the plant oil on them. Oil in the air from a burning plant may cause lung and mouth exposure. Animals may carry the oil on their coat and expose their owners. The urushiol resin may stay on items like coats, balls, and shoes for up to five years and cause an allergic reaction each time the item touches the skin.  

Most people will develop a rash within a day of exposure. Blisters may develop at different rates based on skin thickness and how fast the oil is absorbed. The rash is usually in a streak-like pattern on skin exposed to the oil and may last one to two weeks. Already-formed blisters do not spread the rash. Significant itching and risk for infection may make treatment a good choice. 

Prevention

• Learn to recognize poison ivy and poison oak and avoid them. (Leaves of three, let them be!)

• Wear protective clothing when working or playing in areas where exposure is likely.

• Wash exposed areas with mild soap and lots of water immediately after known exposure.  Cleansing within 10 minutes may prevent rash. 

• Wash clothes and any other items that might have come in contact with the plant as soon as possible.

• Creams and ointments such as Ivy Block® may be used, but these products do not work for everyone.

Can I become desensitized to poison ivy?

No.  Injections and homeopathic remedies have not been shown to be effective in preventing allergic reactions to poison ivy and poison oak.

Treatment

• Apply cool compresses (ice or cold milk) with or without a drying agent like Burrow’s solution

• Oral antihistamines (Benadryl, Clor-Trimeton, etc.) may relieve itching but may cause drowsiness.

• Steroid creams (not ointments) with hydrocortisone may help itching and decrease redness.  Look for steroid creams that do not contain paraben preservatives, which may be irritating on open skin. 

• Avoid using steroid creams on face and genitals or if large areas of the body are affected.

• Calamine lotion or oatmeal baths may help dry the lesions and decrease itching. 

• Antihistamine and anesthetic creams and ointments (products ending in “-dryl” or “-caine”) are not recommended since they may cause skin irritation.