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Spring 2002 Poison Ivy
Poison Ivy (Rhus toxicodendron) and Poison Sumac (Rhus vernix) are widespread throughout the eastern United States. Poison Oak is found in the western part of the country. In our region, backyards, forests and even city parks abound with poison ivy. It grows on the ground and slithers up trees in a hairy vine. The leaves, roots, stems, vines and flowers all contain a resin called urushiol. Contact with the resin will result in an intensely itchy rash of blisters that weep, crust over and eventually disappear within 7 to 14 days. The rash usually appears within 24 to 72 hours after contact. And it itches. It itches so much a song was devoted to it. “Almost everyone is allergic to poison ivy,” said James Banks, M.D., who specializes in allergy and immunology. “With repeated exposures to poison ivy, your body becomes sensitized to it. It’s a T-cell allergic response—so that when you are exposed again, your body recognizes it as a foreign substance and reacts to it,” he said. That’s when the rash develops. Some people have more violent reactions than others, and some say they can roll in it and not get it. Eventually, said Dr. Banks, practically anyone can become sensitized to poison ivy. But only humans are allergic to it. Your dog or cat can loll about in it all day and never take paw to fur. “Once you’ve come in contact with poison ivy, it takes about 10 minutes for the resin to ‘bond’ with your skin,” Dr. Banks said. “If you don’t wash it off immediately, you’re in trouble. If you do wash it off immediately, you may avoid any outbreak, or at least minimize the effects. I’ve had patients say they get poison ivy just by getting close to it, but contact is required.” The resulting rash and fluid-filled blisters are not contagious, contrary to popular belief. Dr. Banks said that the rash is merely the violent reaction—an intense immune response — of your skin coming in contact with the resin. “Once you’ve washed off the resin, you can’t spread it from one affected spot to another place on your body. It just doesn’t happen, despite what so many people believe. You only react to contact with the resin,” he said. The resin, which is invisible to the naked eye, can adhere to anything—your clothes, garden tools, pets and even under your fingernails. Some studies indicate that the resin can remain potent for years on tools stored in dry places. “People who think they are spreading it from one place to another, or from one person to another, are actually coming in contact with the resin somewhere else. It’s a second exposure. That’s why it’s so important to wash your body thoroughly after exposure, and to wash your clothes and tools, as well,” he said. If you are trying to get rid of poison ivy in your garden, never burn it. Breathing the resin or getting it in your eyes can cause dangerous reactions that require medical attention. The best choice is to cover yourself. (Vinyl gloves are best. Rubber gloves actually absorb the resin.) Then wash carefully afterwards. To treat the rash, several over-the-counter (OTC) medications are available. These medications help with the itching, but nothing other than removing the resin quickly will prevent an outbreak. Dr. Banks says mild cases may be treated with OTC medications, but if the itching becomes intense with widespread outbreak, a short course of steroids (prednisone) can greatly reduce the severity of the outbreak. “A five- or 10-day course of prednisone is usually all it takes,” he said. However, more severe reactions might require a few weeks of prednisone to clear the condition. Steroids suppress the immune system, which means that the body reacts less violently to contact with resin. While taken over a long period of time (months) steroids can be harmful, a short course has no lasting effects and can help end the misery of itching. “Let’s face it,” said Dr. Banks, “if you don’t have to be miserable, why put yourself through it.” The only other medication that sometimes is prescribed is an antibiotic. Dr. Banks said that secondary bacterial infections can develop when the skin is raw, and it’s important to watch out for signs of infection. (See box below.) Several OTC ointments to be used prior to exposure have come on the market. Dr. Banks said he doesn’t recommend them—they just provide a physical barrier between your skin and the resin. “But it’s better than nothing,” he said. There also are homeopathic remedies that many pharmacies carry, but he said he hasn’t found one he would recommend to his patients. “The best advice I can give you about poison ivy is this: Stay away from it!” And, yes, cashew nut shells have the same resin coating as poison ivy, but in the course of roasting, the resin loses its potency. TreatmentAfter a known exposure, wash any areas that may have come in contact with the resin within 10 minutes. Wash all clothes, tools, shoes with water and alcohol. If a rash develops, treatments to reduce discomfort include the following:
You should contact your doctor if:
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