In the heat of summer, a walk in the shade shouldn't make my blood pressure rise or my heart pound. But I'm afraid to stray off any woodsy path. Even then I feel like a trapped animal, my senses on alert. I look up, down, right, left. I squint in search of the cause of my anxiety. I rush past the masquerading Virginia creeper, only to stop next to my herbaceous enemy: a vicious three-leafed plant.

If this sounds a bit overblown to you, it's a good bet you don't share my hypersensitivity to poison ivy. If I accidentally brush against it -- or sometimes even if I just stand near it -- my skin tingles. Bumps appear. The rash reddens and grows into blisters that itch incessantly. And even though dermatologists claim the oozing blisters don't spread the rash, I don't believe them.

No matter how careful I am, I get another new bump anywhere I touch. Scratching too hard causes an infection that makes my symptoms worse. Eventually I avoid contact with others; I begin to look like a mummy with gauzy bandages covering the gore. My skin feels so prickly that I can't sleep at night until the blisters scab over. Months later, scars remind me of my ordeal.

How sensitive am I? I can't go outdoors when my neighbors cut their grass; even a cultivated lawn may contain some poison ivy, its seed dropped there by birds and other animals. Once it's mowed, the oil from the plant becomes airborne, and I'm as exposed as if I'd touched it directly.

While my reactions are unusually acute, many are affected by poison ivy. Up to 50 million others in the United States -- 85 percent of those exposed -- get the rash each year, according to the American Academy of Dermatology. (A lucky few don't react, either because their immune systems are otherwise occupied or because their systems don't recognize the alien invader.)

That translates into tens of millions of lost workdays (three days per person is the median), according to the U.S. Bureau of Labor Statistics. Because over-the-counter preparations provide only modest -- and temporary -- relief, poison ivy triggers an estimated 1 million emergency room visits a year, according to one expert. In severe cases, such as those involving firefighters, landscapers, linemen and others who inhale or otherwise contract poison ivy on the job, the problem can be life-threatening; steroid injections must be administered to disable the immune response.

No wonder, then, that research claiming to show better results for a lesser-known treatment has generated some excitement. A study, presented last fall to the American College of Emergency Physicians Research Forum in Boston, showed dramatic symptom relief from a wash called Zanfel. Sold on the Web since 1998 but not approved as a medicine by the Food and Drug Administration, Zanfel has achieved widespread distribution largely on the strength of Internet advertising and word-of-mouth reports, despite its cost of nearly $40 an ounce.

Could a better treatment really be at hand? Alas, experts have their doubts.

Full-Scale(d) Attack

What makes poison ivy so fearsome is urushiol, the oily sap it exudes. The stuff is so potent that a tiny quantity of it -- no more than can fit on a pinhead -- can be enough to trigger a severe reaction in as many as 50 people who happen to come in contact with it.

"Poison ivy is not really a poison," at least not in the same sense that we define other substances as toxic, explained Michael Heller, director of the emergency medicine residency program at St. Luke's Hospital in Bethlehem, Pa., and senior author of the study. "The resin isn't really toxic; it just causes an allergic reaction."

The body's immune system, in other words, overreacts. As is typical in cases of contact dermatitis (the class of rashes you get from touching chemical irritants), it's the defense's heavy artillery -- and not the invader's puny assault -- that causes all the problems.

The process goes like this: Within as few as five minutes of contact, urushiol penetrates the skin, breaking down into chemical derivatives that are easily diffused through the dermal layers. These simpler chemicals bind themselves to skin proteins, changing the cells' appearance. But the disguise doesn't fool the body's T-cells, white blood cells that circulate through the body warding off infection.

Recognizing the invaders (without waiting around to see if they pose any real harm), the T-cells mount a vigorous attack. They migrate to the lymph nodes, where they multiply and produce urushiol-specific antibodies, including inflammatory chemicals like histamines. It's this reaction that produces the ailment's telltale itch.

In case that's not enough defense, the T-cells remember the experience, lying in wait for poison ivy's next attack, whether it's a month or a year away.

What that means is that the next time a sensitized person is exposed to urushiol, the immune system is now at alert, poised to attack. "The primed T-cells migrate back to the area of exposure and trigger the release of chemicals in the skin that cause redness and blistering," said Bruce Brod, a clinical assistant professor of dermatology at the University of Pennsylvania. "These T-cells are like good hunting dogs. Once they sniff the scent for the first time, they can easily home in on it again and again."

To the Rescue?

The study presented last fall showed that Zanfel Poison Ivy Wash, a patented mix of alcohol solubles and soap-like substances made by Zanfel Laboratories Inc. of Chicago, reduces blistering and itching from poison ivy markedly better than plain soap and water. Like Tecnu, an older rival, the product is designed to be rubbed into affected skin, where it binds to urushiol; then it's washed away.

The company-funded study, said Heller, will be submitted for publication later this year to the American Journal of Emergency Medicine.

A randomized, controlled, double-blind trial, it involved 24 participants who had both forearms rubbed with urushiol. All were then treated with Zanfel two, four and six days after exposure. Each individual acted as his own control: one arm got the Zanfel; the other, soap and water. At each interval, researchers compared skin redness, blistering, hardening and itchiness. (The first three parameters were measured using a six-point scale; itch was quantified using a visual analog scale.)

Zanfel emerged clearly "superior to plain soap and water" at every stage tested, said Heller. Zanfel's package claims to offer relief at any stage of the reaction, and often with only one wash.

Some experts are skeptical. "It's not possible for anything to remove the oil's effect a few minutes, let alone a few days, afterward," by which time allergic reactions have already taken effect, said Stephen White, a dermatologist with a private practice in Bethesda. "We know the timing in getting from point one to point two."

Brod, an expert in contact dermatitis and skin diseases obtained in the workplace, agreed.

"Zanfel is no miracle," Brod said. "Zanfel may have a soothing effect on itching and inflammation but cannot wash away the allergen after several days."

Dermatologists agree that the first line of defense against the rash is prompt use of soap and water. Alexander Fisher, a clinical professor of dermatology at New York University Medical School and author of many articles and books on contact dermatitis, wrote in one of his articles, "The poison ivy antigen enters the skin so rapidly that the oil must be totally removed within 10 minutes of exposure."

He further emphasizes that if early washing is not possible, then it is "worthwhile" to wash within the first half-hour to remove any oil remaining on the skin. After that, he said, and others agree, it's too late to remove the irritant.

Heller disagreed. "It doesn't seem like it would work because you wouldn't think any of the allergen [the urushiol] would still be present days after a person was exposed," he said. "But apparently it is. And apparently the body is still responding to the resin that is still present within the skin . . .

"It's sort of like having a reaction to a bee sting days later with the stinger still in; the reaction would get better if you took the source of the ongoing reaction [the stinger] out."

Heller's research team plans additional company-funded studies on Zanfel later this year.

"We plan to check it out under actual conditions, with people who were exposed while working in their yards," he said.

I'd love to believe that relief may be at hand, but I'm not about to volunteer for a firsthand test.

Taking Cover

While the world waits for a perfect remedy, I do my best to avoid exposure.

Even though I may look ridiculous, I wear long sleeves and pants and put my hair in a ponytail before mowing the lawn -- even in humid 90-degree weather. If I need an indoor break, I change my clothes completely and drop them immediately -- sneakers and all -- into the washer. I scrub my face and arms with plenty of soap and cold water. I keep my poison ivy shears separate from my other gardening tools since the oil is so difficult to wash off. I wear two pairs of disposable vinyl gloves when weeding, and I change the outer pair frequently. I wear the same pair of sneakers until they fall apart in the washer.

I've had no need to conduct a personal experiment with Zanfel since I haven't been hit by my personal plague this season -- at least not yet. But a tube is sitting in my medicine cabinet, waiting, just in case. Maybe I'll find relief with this new product, or maybe it will be another dead end for me. So, until then, how do I save my skin after I'm exposed? I've made up my own remedy and learned to "PACE" myself: pamper, apply lotions, cover my blisters and enjoy the sympathy for a while.

And until some groundbreaking research takes place, sympathy is all I'll get. It's probably just easier to treat the rash than to prevent it. Even the National Institute of Arthritis and Musculoskeletal and Skin Diseases is not funding any new research on poison ivy. "There is no known way as of yet to desensitize an individual to this type of reaction," explained Brod.

Other researchers agree.

"As a fellow sufferer, we share the same interest," added Gregory Juckett, an associate professor of family medicine at West Virginia University. "Let me hear of anything new you find."

*

Erika Ginsburg is a Washington-area freelance writer.

An illustrated cross-section of skin shows the immune system's over-response to poison ivy. Round lymphocytes or T-cells rush to the contact site, causing lesions.