Poison ivy, oak, and sumac belong to a family of plants that produce one of the most common allergic reactions in the United States. Experts estimate that up to 70% of the population is allergic to urushiol, the oil found in the sap of these plants. The reaction, known as allergic contact dermatitis or Rhus dermatitis, occurs when urushiol attaches itself to the skin after a person’s direct or indirect exposure to the oil. Direct exposure occurs with contact to broken leaves or stems of the plant. Indirect exposure occurs with touching something that has urushiol on it (like a family pet or garden tool); or through airborne exposure to burning plants.

The symptoms of an allergic reaction to poison ivy, sumac, or oak include the following, from least serious to most serious:

• itching, often intense
• red blotches or rash that can be either raised or flat
• oozing blisters, which may show up in lines
• fever
• headache
• swelling of your throat and eyes
• overall swelling of your body
• general feeling of discomfort
• stomach cramps, nausea, vomiting, and diarrhea.

If you have been exposed to poison ivy, oak, or sumac:

• Cleanse: Immediately cleanse the area with plain soap and water, paying special attention to the palms of your hands. Since this outer layer of skin is thicker, urushiol does not penetrate the area and can be carried on the palm for hours. Also wash under your fingernails. Urushiol will bind to the skin within 5 minutes to 2 hours after exposure. After binding, plain soap and water are no longer effective at removing urushiol.
• Decontaminate: Remove and hot-water wash all clothing, shoes and shoelaces that may have come in contact with the oil.
• Relieve: Zanfel (®) can help remove residual oil as well as relieve itching. Over-the-counter steroids, such as hydrocortisone will only help mild reactions. Apply cloths soaked in cool water or aluminum acetate solution (Burow's solution), then calamine lotion or ointment to reduce the redness, ease the itching, and help dry up the blisters. One can take lukewarm baths with cornstarch (1/2 cup) or colloidal oatmeal added to ease the itching. DO NOT use topical antihistamines (diphenhydramine) or creams containing anesthetics (benzocaine). Cover any oozing blisters with a clean gauze bandage soaked in a baking soda and water solution.
• Don’t scratch: Scratching may cause infection because it allows bacteria from dirt on the hands to enter the skin. Excessive scratching may also cause scarring.

If the rash spreads to your face, mouth, eyes, or genitals, or if you develop a fever, headache, extreme redness, pus, or other severe symptoms, see your doctor. He or she will recommend one or more of the following:

• Applying corticosteroid ointment or cream to the affected areas two to three times a day, gradually reducing to once a day
• Taking oral corticosteroids such as prednisone
• Taking oral antibiotics or using an antibiotic cream if an infection develops.
• Follow these guidelines to help prevent poison ivy, oak, or sumac:
• Know what the plants look like and where they grow so you can avoid them.
• Wear long-sleeved shirts and long pants, hats and gloves if you are going to be in an area where these plants grow.
• Within 5 to 10 minutes of contact with the plant, rinse exposed skin thoroughly with soap and water (or just water). Be sure to clean under your fingernails.
• Wash clothes and shoes in hot water and detergent to remove any oil that may be on them. Wash any other outdoor items frequently (tools).
• Give any outdoor pets a bath if you think they have had contact with the plants.
• Do not burn any suspicious plants, since inhaling its smoke can cause a deadly systemic reaction.

Dr. Larrabee is Associate Director of Family and Community Medicine at the Walter L. Aument Family Health Center, 317 S. Chestnut St., Quarryville.