How to avoid an itchy summer - avoiding poison oak

Sunset, July, 1995 by Peter Fish

Poison oak is waiting for you. But you don't have to be a victim

We've all heard the stories. A hiker ventures off the trail. Campers look for brush to build a bonfire. A pet lover hugs her dog when he returns from a jaunt in the woods. From these innocent beginnings, the tales acquire a horrific, Stephen King quality. Within hours, the hapless victims morph into monsters - itchy, red, swollen, blistering monsters - all on account of poison oak.

Poison oak is probably the West's most common outdoor hazard. Granted, it doesn't rank up there with rocky cliffs and grizzly bears. On the other hand, as you lie soothing yourself with cold compresses, a grizzly attack can start sounding pretty good. So, to avoid finding yourself in such a mess this summer, take time to recall old poison oak lessons - and learn a few new tricks.

MISNAMED MENACE

Western poison oak (Toxicodendron diversilobum) is not a real oak. It belongs instead to the cashew family, as do its relatives, poison ivy and poison sumac. Found solely in the West, poison oak grows from southern British Columbia to northern Mexico. In California it is one of the most ubiquitous native shrubs: you can find it clinging to coastal bluffs, coiled beneath oaks and redwoods, and spreading luxuriantly along creeks and streams. In fact, almost the only places in California where poison oak can't be found are deserts and elevations above 5,000 feet.

Recognizing poison oak can be difficult because the plant can take a number of forms: freestanding shrub, vine, ground cover. That old rhyme "Leaves of three, let it be" is a help: leaves do generally grow in clusters of three. They're thin, shiny, and oak-shaped. Green in spring and early summer, leaves turn deep red toward fall, then drop off entirely, revealing grayish branches decorated by white berries.

The leaves, stems, and berries all contain a chemical compound called urushiol. Folktales to the contrary, poison oak doesn't exude poison: you won't get a rash just by walking near a plant. But because urushiol oozes up through even tiny cuts on leaves and stems, just brushing against poison oak can get the chemical on your skin.

Then, within minutes, the urushiol will have entered your inner skin layer, the dermis, where it bonds with antigen cells. These antigens migrate to your lymph nodes. The first time this happens, you might not get a rash. But the immune system has been primed so that at a later exposure - often only the second - the body will treat the urushiol as a foreign invader. The immune system rushes T cells to the site of the invasion, where they begin releasing chemicals to destroy the urushiol. Unfortunately, these chemicals also destroy the surrounding skin. And so starts the reddening, the itching, the swelling, the blistering.

As any poison oak sufferer knows, what is especially maddening is that the rash seems to spread far beyond the part of the body exposed to the plant. Possible explanations for this phenomenon are offered by poison oak expert Dr. William Epstein, professor of dermatology at the University of California at San Francisco. First, urushiol is easy to spread. If it is on your hands, anywhere you touch will be vulnerable. Urushiol can also be picked up secondhand from clothing, boots, even car seats and steering wheels. Second, many immunologists believe that urushiol puts the whole lymphatic system on alert, sending T cells throughout the body. Parts of the body that have suffered earlier outbreaks may be prone to breaking out with every new one.

An estimated 50 percent of Americans are clinically sensitive to poison oak. Another 10 to 15 percent are fully immune. That leaves 35 to 40 percent classified as clinically subsensitive, meaning that they can go along for years, blithely believing themselves immune, until their day of reckoning. "We see this every year," says Epstein. "These are people who for years pulled up poison oak, cleaned up gardens for their neighbors, never had any trouble. Then, when they come to see us, they've got the worst case you ever saw." Such late-blooming sufferers get more bad news, says Epstein. "When you switch over, you never go back."

HOW TO TREAT IT

Savvy outdoorspeople know the standard ways of avoiding exposure to poison oak. They know that wearing long-sleeved shins and long pants offers some protection in poison oak country - but only some. They know that pets, notably dogs, often pick up urushiol on their coats when outdoors and should not be touched until bathed. They know that some of the worst cases of poison oak come from inhaling smoke, so they gather their firewood carefully.

Still, almost all hikers and gardeners will eventually discover that they've blundered into a thicket of T. diversilobum. What then?

Your best hope is to wash the affected areas immediately with lots of cold water. Then, as soon as you can, wash the areas again with an organic solvent like rubbing alcohol (or a commercial urushiol remover like Tecnu Poison Oak-N-Ivy Cleanser), followed by more cold water. If performed speedily enough, this first aid may well prevent an outbreak.