Eager to startflyfishing New York's Croton River, Jay Cassell hiked a half mile to the wateron a cloudless spring day. Four hours and the same number of brown trout later,he trekked back to his car, reenergized by his midweek brush with nature. ButCassell, FIELD & STREAM deputy editor and a lifelong outdoorsman, had noidea how devastating this encounter would prove to be.

"Within 24hours," he recalls, "blisters had broken out all over my face and arms,even between my fingers. My eyelids were so swollen I couldn't see. My lipswere so bad I had to drink liquid food through a straw. I looked like apunching bag for George Foreman."

At the ER, adoctor gave him a cortisone shot to begin counteracting his extreme allergicreaction. Despite this, Cassell couldn't work for a week and devoted all hiswaking hours to soaking the maddening lesions in an oatmeal bath as hot as hecould stand it. It was two weeks before he felt normal again.

Some 60 differentspecies of poisonous plants, or toxicodendron, pose a risk in North America.The most common are poison ivy, poison oak, and poison sumac. Though a smallhandful of people appear to have natural immunity, the majority of us—85percent or more—can count on an unpleasant reaction after exposure to urushiol,the culprit sap produced by these plants. For Cassell and other extremelysensitive people (an estimated 10 to 15 percent of the population), as littleas 50 micrograms (less than a grain of salt) can precipitate a fortnight oftorture.

PREVENT IT

The best defenseagainst poison plants is limiting your exposure in the first place, but evenexperts have trouble identifying such a ubiquitous enemy. "I've written abook chapter on toxicodendron and emergency medicine," says Dr. StevenStephanides, an ER doc and peer reviewer for the Wilderness Medical Society'sjournal. "I still got poison ivy last summer."

Stephanidesrecommends the following strategies to reduce exposure:

• Don't rely onthe "leaves of three, let it be" rule. Poison plants can vary greatly in appearance between different geographicalregions and depending on the time of year. Leaves differ in color and size, andidentification can be especially tricky in the fall. Ask a local guide to showyou exactly what you need to stay away from.

• Dress right. Wear long pants and socks whenever you're hiking in poison-plant territory.

• Avoid secondaryexposure. Urushiol is a fiendishly stubborn compound that reportedly can stay potent foryears. Once the resin has contaminated your fishing gear, clothes, or even yourdog, it can be transferred to you. Wash or hose down any potential sources ofcontamination.

• Don't burnbrush. Some of the nastiest run-ins with poison plants occur when urushiol becomesairborne in smoke, allowing it to penetrate the eyes and lungs. "This israre," says Stephanides, "but it can be life-threatening. You've onlygot one airway. If you get too many blisters there, it makes breathingdifficult."

• Lather up. Apply products like IvyBlock on any uncovered skin. This may provideprotection, as long as you reapply if you sweat.

TREAT IT

If avoidancefails, treatment can range from over-the-counter products to a trip to thedoctor for steroids. It all depends on the severity of your symptoms.

• Start withwater. Your efforts at lessening the effects of contact with a poisonous plant canstart in the field. Urushiol appears to require 10 to 20 minutes to penetratedeep inside the skin. Soap is helpful, but water, especially if applied within20 minutes of exposure, can usually prevent a bad reaction. Jumping in a streamand washing the stuff off will help.

• Try the oldstandards. If a rash still develops, use an itch-stopping agent like calamine lotion,which can also help keep scratched skin from becoming infected. Calamine issometimes sold blended with an antihistamine similar to that found in productslike Benadryl, which could also lessen the effects of the allergic reaction.But don't just take whatever treatments you can get your hands on. "Everynow and then," says Stephanides, "we see a patient who lathers himselfup with calamine, then takes a high dose of Benadryl orally, and ends up havinga toxic reaction from this combination."

• Take a bath. Soaking in hot water can also reduce itching, possibly by triggering therelease of natural antihistamines or by interrupting nerve transmissionpathways from the skin to the brain. If your rash develops into weepingblisters, and either Burrow's solution or Aveeno oatmeal bath treatment to thewater. Another OTC product, aluminum acetate, can be used in compresses to dryout the lesions. But the belief that touching the blisters will spread poisonivy around the body is a myth.

• Get somehelp. See a doctor at the first sign of a severe reaction (nausea, stomach cramps, orexposure of sensitive body parts like the eyes, groin, or lungs). Stephanideshas twice had to treat anglers who got into severe trouble after using poisonivy leaves as toilet paper.

• Pop a pill. The gold-standard treatment for severe cases is prednisone, a prescription formof cortisone. If your doctor prescribes these pills, make sure to take theentire course, or the worst symptoms may bounce back. "Once urushiol haspenetrated deep inside your skin," says Stephanides, "it takes a weekor longer for your immune system to eliminate it."

• Grow older. There's evidence that the aging process reduces sensitivity to poisonplants.

For his part,Cassell says he has become both older and wiser when it comes to toxicodendron."It's sunk in that I need to be extremely careful. If there are poisonplants by a stream and it's a good stream, I'm still going to fish it. But I'llmake sure I don't touch a damn thing."

RUB IT IN

A variety of barrier creams offer new hope to outdoorlovers. Do they work? Several studies, including one at Duke University, foundthat the answer is yes—in a lab. A few new products rated as having "goodefficacy" include IvyBlock, Hollister Moisture Barrier, Stokogard, andHydropel IV Block. But Stephanides says that no one has studied them in thefield. "These creams probably work somewhat, but there's no perfectsolution to poison plants." Of these, you might want to try IvyBlock, theonly one that is FDA-approved. It retails for about $15 at most pharmacies. —JIM THORNTON