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Increased carbon in atmosphere may explain bumper crop of poison ivy

By Laura Hambleton
Special to The Washington Post
Tuesday, August 31, 2010; HE01

It started with a slightly puffy eyelid in early summer, which I waved off as an inconsequential bug bite. The next morning, I couldn't ignore my son's symptoms when he appeared with two eyes swollen to slits, a bloated face and an itchy rash raging over his body.

Ah, poison ivy. How it torments with weepy rashes and maddening itchiness -- and may do so more and more.

That is what the experts say, and I can offer supporting testimony, at least for this season's crop.

"It is a good year for poison ivy," said Alonso Abugattas, the acting director of the Long Branch Nature Center in Arlington. "We've noticed it more in our park. I think it's the timing of the rain."

Or it may have to do with increasing carbon dioxide, or CO2, levels in the atmosphere, said Jacqueline Mohan, an assistant professor at the University of Georgia's Odum School of Ecology. According to a report in the journal Environmental Health Perspectives last year, the amount of CO2 in the atmosphere has grown by 22 percent since 1960, which may not be so good for humans but is great for poison ivy and other vines.

Mohan has been tracking poison ivy since 1998. In a study in the Duke Forest in Durham, N.C., she simulated the carbon dioxide content in the air 50 years ago, today and using projections for the year 2050. "Tree seedlings grew 8 to 12 percent more, with more C02," said Mohan. "Poison ivy grew 149 percent more. Poison ivy is getting bigger, faster and nastier."

Plants survive by converting carbons from carbon dioxide into carbohydrates through sunlight-fueled photosynthesis.

"Vines are particularly adapted to take advantage of higher CO2 in the atmosphere," said Mohan, since they "can increase their rate of photosynthesis to make more green leafy tissue," which allows them to grow more and put out even more leafy tissue. Trees, on the other hand, "have to devote much of their photosynthetic carbohydrate to creating woody, non-photosynthetic support tissues such as trunks and branches, which do not lead to further increases in photosynthesis."

Sprouting everywhere

Poison ivy is in the same plant family as cashews, pistachios and mangoes, which also cause skin reactions in some people. Native to the East Coast, the vine has shiny, dark-green leaves, often serrated and clustered in threes. In the fall, the leaves turn a handsome scarlet, prized by some botanical gardens. And birds are fond of its berries, which start out green and turn white. The vine grows along the ground, climbs up trees and can become a massive, hairy rope; in some cases, it buds into a bush.

"It can sprout and grow just about wherever seeds contact soil," said Jon Traunfeld of the University of Maryland Extension Service. "It can grow in deep shade or full sun."

Most people are allergic to the oil poison ivy produces, urushiol. The oil is present in all parts of the plant -- stems, berries and leaves -- during any season, which means that if you are working in the garden in the middle of November or bushwhacking through the woods in winter, you could develop a rash from coming into contact with poison ivy roots or some other remnant of the plants. Burning logs that are covered in poison ivy can cause respiratory problems for people who breathe in the smoke.

"Even in dead poison ivy the oil is still active," said Georgetown University professor of nursing and health studies Laura Anderko, a registered nurse with a PhD in public health. The age of the plant doesn't matter. "The Japanese have a 500-year-old poison ivy specimen that can induce a rash," said Lewis Ziska, a plant physiologist with the U.S. Department of Agriculture.

Poison oak, which is found mostly out West, and poison sumac, which thrives in wet boggy areas in the mid-Atlantic, elicit similar reactions.

To illustrate just how prevalent poison ivy is in the region, Ziska offered a tour of the USDA's 2,000-acre farm and research center in Beltsville on a recent sticky August afternoon. He parked his car and knelt by a tangle of poison ivy intertwined with other vines -- Japanese honeysuckle and Virginia creeper -- growing alongside a field of corn.

"You have to see past the green," Ziska said. "We are seeing essential changes to plants. Fifty years ago it was rare to find trees with vines growing all over them. Now it is common. We think it is due to the competitive ability of vines with the additional CO2."

We drove to the south farm, where Ziska pointed again to poison ivy, Japanese honeysuckle and Virginia creeper smothering a fence. "Land use has changed," Ziska continued. "We now have fragmented pieces of forest instead of areas of deep shades. We are creating preferential environments for vines, making conditions ripe for them to grow in places they've never been."

Also, he said, the vines themselves are changing: "The poison ivy oil is not just oil; it has different chemicals, like cholesterol. It has unsaturated and saturated oil. The ratio is changing and the oil is more virulent."

The Duke study, which Ziska also participated in, analyzed the makeup of urushiol in the poison ivy leaves grown at various concentrations of carbon dioxide. The researchers found that poison ivy leaves exposed to more carbon dioxide were more virulent because they had more urushiol and that the form of the urushiol was a more allergenic one (with unsaturated triple carbon-carbon bonds, instead of saturated single carbon-carbon bonds) that Mohan said "may make it easier for urushiol to interact with human cells."

The impact of a hardy, more prolific and potent poison ivy on humans would seem obvious: more-frequent and more-severe rashes. But Donald K. Milton, a public health physician and director of the University of Maryland Institute for Applied and Environmental Health, said that isn't a sure thing. "When I was a kid in Baltimore, we played in the ravines among the vines," he said. "Nowadays kids spend their time indoors playing video games. There may be more poison ivy, but our data says people are spending less time outdoors."

Scene of the crime

The noxious plants didn't cross my mind when I took my 13-year-old son, a friend of his and our dog for a walk in a patch of woods along a deep creek near our Chevy Chase home. The two boys and the dog ran off the trail, pushing through chest-high foliage to get to the creek and its swimming holes.

My son's quick and severe allergic reaction a day later was a surprise. After applying calamine lotion and trying other home remedies, it was clear we needed expert help.

The clinician at our local CVS Minute Clinic literally gasped when she saw his swollen eyes and face and suggested we head right away to an emergency room. We went instead to a walk-in clinic in Bethesda run by family physician Kerri Gray. She prescribed oral steroids, and topical and oral antihistamines including Benadryl.

"And get cold," advised Gray, who has been practicing for about 15 years. "Use ice cubes, cold compresses on your skin and keep the house cool. I am seeing a lot of poison ivy this summer. Patients are telling me they are seeing poison ivy where they've never seen it before."

After his outbreak, my son spent a week inside, embarrassed by his swollen, alien-from-outer-space looks. We upped his steroids at one point because the rash continued to spread. The swelling responded fairly quickly, but it took weeks for his rash to finally fade. My son's friend had an equally severe case, requiring similar treatment.

My son has sworn never to return to that wooded spot and never to touch anything that looks like clustered three-leaves of poison ivy again. That wariness is warranted. People have different sensitivity to poison ivy -- some people can touch it and be fine -- but once sensitized, experts say, a person's subsequent reaction is likely to be more severe.

"Clinically every time you get exposed to the plant, the reaction will get worse," said Jihad Alhariri, a dermatologist on the faculty of Johns Hopkins Medical School. "The mainstay is avoidance: Identify the plant and avoid it. If you get in touch with it, the best [thing] is to wash the area immediately. After one hour, the oil crosses the epidermis and you are exposed to it. Eight hours down the road, you can get blisters."

Typically, the rash shows up as bumps, often in a cluster or line, that grow and then ooze. "Where you get the rash depends on the method of exposure," Alhariri explained. "You could get linear streaks on exposed areas. If you just brush the vines while doing gardening, you can get it on your arms, face, eyelids and lips. It could be a mild rash, or the hives can turn into swollen blisters that burn and are severely itchy."

Georgetown's Anderko offered a theory about my son's case: "To get a full-body reaction, it is possible that your son touched oils on the dog, his clothing, or the oils on his skin where he was originally in contact with the plant, then spread it onto more areas of his body," she said.

Poison ivy is not contagious, nor does scratching spread the rash. Direct contact with the oil is the only way to start an allergic reaction.

And, as Anderko pointed out, the oil stays on clothes, shoes -- and dogs -- until you wash them.

"People let their dogs run through the woods and then they pet their dog," oblivious that they may be exposing themselves to poison ivy, said Abugattas, of the Long Branch Nature Center."

When the University of Georgia's Mohan goes hiking, she brings along rubbing alcohol, which she uses if she thinks she has touched poison ivy. She takes other measures, too, that anyone thinking of taking a late-summer walk in the woods would be wise to consider. "I wear long pants and long sleeves. When I am working in the woods, I wear a triple layer of gloves duct-taped to my sleeves. When I get home, I put the clothes in the washing machine, go take a shower -- and then pray."

Hambleton is a freelance writer, editor and documentary filmmaker in Chevy Chase.

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