...Or poison sumac or poison oak--the nasty threesome of the plant world of North America. Poison ivy is found in the East; poison oak in the West; poison sumac in the South. All three grow leaves in threes, with the middle leaf extending further than the other two. And all are members of the plant genus Toxicodendron. Note the prefix "toxic" in that name. That's because all three also contain a potent oil, a colorless or light-yellowish oil call urushiol. Found in the leaves and vines of these plants, even tiny amounts of urushiol can trigger a severe allergic reaction in about 50 percent of adults in the United States. Most people first develop redness at the point of contact, anywhere from a few hours to perhaps even two weeks after you brush against one of the offending plants. In highly sensitive individuals, swelling and blisters follow, along with a maddening itch. The torment typically lasts for two weeks, and in its final stages the urushiol-caused rash will form an attractive, scabby crust as the blisters burst.
Once you've been hit with urushiol, few medications work. Most over-the-counter remedies for skin rashes, such as hydrocortisone ointments, are too weak to do much good. Antihistamines and anesthetics, in fact, will only make things worse. A few people report that calamine lotion helps. Same for warm baths in water to which you've added Aveeno brand oatmeal, which seems to soothe the area. Cold, wet pads also may relieve the itch. But the best solution is a strong, anti-inflammatory topical steroid -- something only a doctor can prescribe -- or a steroid that is taken orally. Using one of these treatments, most symptoms will disappear or lessen within 24 hours.
Urushiol is remarkably persistent and nasty stuff. It can stay potent for years. And wearing long-sleeve shirts and long pants is not certain protection: Brush against an urushiol-bearing plant, and the oil will adhere to the fabric. Touch the fabric, scratch your ear, and in a day your ear has mysteriously become a huge, weeping blister. Your pets also can turn into urushiol magnets, so petting a dog or cat that has walked through poison ivy will result in red, swollen hands.
With all that, it's clear that avoidance is the best solution. Know what the offending plant found in your area looks like, and do your best to stay away from it. It's also possible to apply a urushiol "barrier," which is sort of like sunblock. One such product is IvyBlock, manufactured by Enviroderm Pharmaceuticals and available in most drugstores. IvyBlock contains a chemical -- bentoquatam - which prevents the urushiol oil from penetrating the skin. It's recommended that you apply IvyBlock at least 15 minutes before the risk of exposure, then again every four hours.
If you do happen to stumble through a thicket, and haven't taken precautions, the key is to act fast: Cold water, and lots of it, will usually remove the urushiol before it can soak into the skin, IF washing begins within a few minutes of contact with urushiol. (If you're not real sensitive, you may be able to wash away the urushiol as long as two hours after exposure.) Don't use warm or hot water -- that will spread the oil and open skin pores to let the stuff in. Soap also can help wash away the urushiol. Better yet is a solvent such as alcohol or gasoline. Gasoline can burn the skin itself, so don't leave it on for more than a few seconds without washing with soap and water.
Nasty things, those Toxicodendron plants. One can only hope that exposure to them is infrequent, and minimal.