Poison Ivy

It was Tuesday morning, July 5th, and I was on call the day after the holiday weekend. In only the first 30 minutes of the day, we received 5 emergency calls for rashes from the weekend. Summer had officially arrived and with it came picnics, barbecues, hiking, gardening and of course, poison ivy.

These blisters form a line in the same pattern as the poison ivy leaf rubbing against the skin

The typical poison ivy rash is caused by urushiol, the same oil found in poison oak and sumac. The oil is found in every part of the plant, including the leaves, stems and roots. It is absorbed into the skin within minutes of exposure. The first time you touch urushiol, you might not develop a rash. With repeated exposures, however, your immune cells recognize the oil as foreign and launch an immune attack that causes the itching, redness and blistering of the skin that make you regret your outdoor adventures in the woods. Many people develop a more intense reaction with each exposure that occurs. Although some people claim that they are “not allergic to poison ivy,” there is no way to be sure. After many rash-free exposures year after year, your immune system may kick in and make you wish you hadn’t been so confident!

Most rashes from poison ivy go away on their own within a few weeks. For a mild rash, discomfort can be treated with over-the-counter hydrocortisone cream or calamine lotion applied topically. Creams containing menthol or camphor may help soothe the skin but won’t speed the resolution of the rash. Cool cloths, showers, oatmeal baths and compresses with astringents such as Domeboro may also help alleviate the itch. Oral antihistamines like Benadryl work beautifully at relieving the itch but might make you drowsy. Newer antihistamines such as Zyrtec and Allegra also help with symptom relief and usually cause much less sleepiness. Many patients find it useful to take Zyrtec or Allegra in the daytime while they work or take care of the kids. They then use Benadryl at night when the itching is often worse and fatigue is not a problematic side effect.

Serious reactions, however, require treatment. You need to see a physician if the itch is severe, continues for more than a few weeks, spreads over most of the body, or is associated with swelling of the eyes or face. An uncommon complication of poison ivy is infection, which is usually accompanied by fever and pus, pain, or warmth of the affected skin. If any of these develop, you should definitely schedule an appointment to see your doctor.  I often prescribe patients topical steroids stronger than the ones available over-the-counter to make them more comfortable and help speed healing.  If the rash is extensive or unusually severe, systemic steroids like prednisone may be needed, however there are potential side effects to these oral medications.

One thing that you do not need to worry about is passing the rash on. The rash is not contagious and does not spread from one area to another.  While it might seem like the rash is spreading, this is a delayed response to the initial poison ivy exposure. Unfortunately, by the time the rash appears, the damage has already been done! Scratching does not make the rash spread, but it may irritate the skin and increase the chances of infection or other complications.

Patients (and parents of patients!) often ask me how to prevent the rash associated with poison ivy. Obviously, the most effective preventive measure is to stay away from the plant that causes it. These plants are found all over the United States. Typical locations include the woods surrounding your house, in the garden, and along the side of the road. Both poison ivy and poison oak grow in clusters of three leaves. Poison sumac, however, has long oval leaves in clusters of 7-13 leaves angled upward on a stem.  The saying “Leaves of three, let them be” should help remind you how to identify the plant, but unfortunately unless you moonlight as a botanist, it isn’t always easy to tell.

“Leaves of Three” configuration associated with poison ivy

When you anticipate spending time in area where poison ivy grows, you should wear protective clothing that covers your arms and legs. Heavy duty vinyl gloves are recommended when you have to touch the plant, as rubber is not protective. Better yet, if you can, hire a professional to help. Remember that even dead poison ivy plants often contain the nasty urushiol that you need to avoid. If you believe that your skin has contacted the plant, wash immediately and thoroughly with soap and water. Immediate washing can prevent the rash, but waiting even 10 minutes to wash will decrease the amount of oil that can be removed by 50%. Oil residue may linger on clothing, pets, sports equipment or toys, and these should be washed as well to prevent further exposure. In fact, exposure to contaminated equipment, tools, and clothing is the primary cause of poison ivy rashes, rather than direct contact with poison ivy itself.

Since poison ivy typically grows in locations where you will be unable to wash immediately, there is great interest in finding compounds that can be applied hours after exposure to remove the oil from the skin. Products such as Tecnu, Zanfel and Ivarest claim to bond to urushiol and eliminate it, but these products have not been scientifically proven to help.

Poison ivy is one of those summertime pests that can affect any of us. Thankfully it’s unusual for poison ivy to cause serious complications, but it is a notorious cause of some unpleasant summer days or weeks. If you pay attention to your surroundings and follow the tips presented above, chances are that you will have a relatively itch-free summer.


Treatment options for Poison Ivy


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