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CORVALLIS, Ore. - More than 70 percent of Americans will take to the outdoors this year and 12 million of them will return home with a nasty itch from poison ivy or poison oak, according to Oregon State University pharmaceutical researcher John Mark Christensen.

The culprit is urushiol (pronounced ooh-roo-sheeall), says Christensen, an associate professor in OSU's College of Pharmacy. A clear, oily substance found in every part of the plant, urushiol is harmless until it starts to oxidize and eventually kicks the body's immune system into action, starting a battle that can turn into a painful, debilitating rash.

There are a number of methods for getting rid of the irritant and stopping the itch, Christensen said, ranging from simple soap and water to specialized cleansers that bind with the oil and remove it from skin.

What works best?

Christensen delved into the properties of the toxin, eventually developing a specialized skin cleanser that went on the market about a year ago, but he says soap and water can be just as effective.

"It's really simple," he said. "If you are diligent about washing off the oil with soap and water, that works just as well as any of the cleansers that are out there on the market. The problem comes about because most people just aren't diligent enough in their cleansing routines.

"If you don't do the due diligence required to clean off the urushiol from the skin," Christensen added, "that's where you'll run into trouble."

Teaching an upper division class in the science of cosmetics, Christensen has in many past classes challenged students to remove various cosmetic preparations from the skin. Students vigorously attack the chore, only to find that their efforts consistently fall short.

"Most people just don't do that through of a job of cleansing," he pointed out. "With poison oak or ivy, the ideal is to cleanse the area immediately once you realize you've been exposed."

Using lots of soap and water and keeping water temperatures as close to skin temperature as possible - about 91-93 degrees - give the best odds for success, he says. Specialized cleansers designed specifically for poison oak and ivy do work well, he added, quickly binding with urushiol and unlocking it from the skin.

Anyone hoping for a vaccine against the itch may have a long wait, Christensen said.

"A vaccine to prevent the reaction is certainly possible, but what it comes down to is economics. There are about 10-12 million cases a year and that's not a big enough market to attract investment from pharmaceutical companies. Developing vaccines is very pricey and you'd have to be talking about sales of 50 to 100 million doses per year before a pharmaceutical company could begin to recoup research and development costs as well make a reasonable return on their investment."