Dear Doctor Column, May 16, 2005

Preventing Rash Better Than Curing It

Question:

I invariably get poison ivy every spring when I begin to work in the yard. My friend told me about a product you put on before you go outside. Does it work? What can I do to minimize my chances of getting exposed every year?

Answer:

Poison ivy is a term often loosely used to refer to an entire class of plants comprised mainly of poison ivy, poison oak, and poison sumac, all of which can cause allergic skin reactions. Some form of these plants grows almost everywhere in the United States except Alaska, Hawaii, and some parts of Nevada.

When it comes to dealing with the itchy, flaking skin, red rashes, and oozing blisters caused by exposure to poison ivy, oak, and sumac, you're not alone. Each year, 10 to 50 million Americans develop an allergic reaction to poison ivy, oak, and sumac — the most common cause of allergic rashes in the U.S. and a leading cause of occupational dermatitis for outdoor workers in many areas of the country. The first exposure to these plants rarely causes a problem, but can alter sensitivity of the immune system so subsequent exposures cause the typical allergic rash.

Your friend might have been referring to IvyBlock®, the first product approved by the U.S. Food and Drug Administration to help prevent the rash (contact dermatitis) caused by contact with these plants. Available since 1997, the over-the-counter lotion contains bentoquatam, which forms a visible, chalk-like barrier against an oily substance in the plants — called urushiol (you-roo-shee-ol)— that causes the rash. The lotion must be applied at least 15 minutes before possible contact with the poisonous plants and reapplied every 4 hours for continued protection.

If you use IvyBlock, UAB experts suggest that you do so in addition to traditional preventive measures, which include wearing gloves, long-sleeved shirts, and long pants when working outdoors. If you think you have come in contact with poison ivy, oak, or sumac, wash the area thoroughly, including under your fingernails, with regular soap and warm water as soon as possible to remove the oily chemical. The longer the resin stays on the skin, the worse the reaction is likely to be.

In addition to washing your skin, don't forget to thoroughly wash garden tools or any other implements you might have been carrying or using when you came in contact with the plants. Bathe the family dog and cat, as well, since they can carry the sensitizing resin on their fur.

Poison ivy and oak rash may begin as an area of blister formation accompanied by stinging and itching. The blisters often appear in thin lines where the person has brushed against the plant. The blisters then break and drain a clear yellow fluid for a period of time (determined by an individual's sensitivity). Contact with the fluid will not spread the rash, since it does not contain urushiol. Crusting occurs as the fluid dries. Healing generally takes place within 2 to 3 weeks.

If, despite your best efforts, you break out in a rash, try applying a paste of baking soda or Epsom salts and water, or use calamine lotion or nonprescription hydrocortisone cream for the itching, which can be excruciating. Do not place alcohol on affected skin, which tends to worsen the problem. Cover open blisters with an antibiotic ointment and a Band-Aid or sterile gauze to prevent infection. Soothing creams and lotions will not help much when blisters are open, but they can be used again when the blisters close.

Try not to scratch, although we know that's easier said than done. Scratching increases risk for infection. If itching becomes severe or the rash covers large parts of your body, see your doctor, who may prescribe a stronger cortisone ointment or pill and an antihistamine.