Extra: Watch Keith Killingbeck, a botanist who teaches at the University of Rhode Island, talk about some of the largest poison ivy bushes he has ever seen, in the Marsh Meadows Wildlife Preserve in Jamestown, at projo.com/video

At some point –– in between the interminable nights spent scratching her welts and the days of dousing them with rubbing alcohol –– Deborah Rosen walked into her Kingston backyard to investigate the poison ivy patch responsible for her misery.

She’d had a few minor outbreaks over the years. But this spring’s reaction was so severe she would eventually camp outside a closed clinic on a Saturday morning waiting for a doctor’s help.

What she found in her backyard surprised her –– but not some scientists.

“I saw way more of it than I’m used to seeing,” she said. “I hadn’t consciously looked because in the past I hadn’t had it that bad, but it was growing like gangbusters. It seemed there were more vines than in prior years.”

Could poison ivy be one of the big winners of climate change?

Lewis Ziska, a plant physiologist with the U.S. Department of Agriculture, in Maryland, thinks so.

In two laboratory studies he conducted in 2007, poison ivy plants virtually doubled in size and their itchy oil became more potent when the test plants were grown in atmospheres of increased carbon dioxide.

If the research findings are correct, carbon dioxide –– which is emitted into the air naturally through carbon deterioration and through such human activities as burning fossil fuels –– might be the equivalent of growth hormone for the irritating weed.

Carbon dioxide levels in the atmosphere have increased about 20 percent since 1970, Ziska said.

“The work we’ve done with poison ivy seems to show a strong response to more CO2,” which all plants absorb as a food source. “Combine that with warming temperatures and milder winters and that may also favor poison ivy.”

Says Ziska: “We’re hearing apocryphal stories from the Northeast –– ‘We’ve never seen so much poison ivy. What’s going on?’ ” But Ziska says his research is inconclusive as to why poison ivy –– and perhaps other vine plants such as English Ivy –– may be flourishing.

“Most of what we’re seeing is from lab tests. What we haven’t done, because of a shortage of volunteers, is go out and actually survey poison ivy around the country,” he said.

In other words no one wants to … touch the subject.

“It’s hard to get people excited about getting out and doing field work on poison ivy.”

Local hospitals keep no readily available statistics of patients seeking relief from poison ivy. Anecdotally, some emergency rooms report no increase while at Rhode Island Hospital, emergency room doctor Selim Suner says, “It seems like we are seeing more. We haven’t done any official tally but, just from working in the emergency department, there has been an increase in the number of cases.”

Suner, who has worked at Rhode Island Hospital for 15 years, says “usually people come in because they are at wits’ end from the itching. They want some relief. We’ve also seen some severe cases as well” this spring “involving the throat and lungs, inhaling the toxin, especially after weed-whacking.”

About 80 percent of people are allergic to the oil from poison ivy plants called urushiol.

The oil, if not washed off within 15 or 20 minutes, will be absorbed into the skin. The body’s immune system attacks the oil, which prompts the rash, blisters and itching. A bout of poison ivy can last two weeks or more.

In severe cases, a doctor can prescribe a steroid such as prednisone –– which blunts the body’s immune system and stops the white blood cells from attacking the oil –– and can suggest an antihistamine such as Benadryl to ease the itching.

Keith Killingbeck has suffered from poison ivy only a few times in the 30 years he has taught botany at the University of Rhode Island, taking students out on regular field trips around Rhode Island.

Killingbeck says poison ivy is flourishing but he is skeptical whether increased carbon dioxide is the reason; some other studies, he says, suggest that spikes in plant growth from increased carbon dioxide eventually subside over time.

The more likely cause, he believes, is the continual clearing of the land, the opening up of the forest canopy, which improves the environment where poison ivy thrives.

“Certainly poison ivy is a plant that grows well in highly disturbed areas and more and more areas are becoming highly disturbed.” Particularly with development.

“So if there is a general observation it is that poison ivy is growing in more places, growing more vigorously. What that is attributed to, could be anyone’s guess.”

Killingbeck holds some admiration for poison ivy, a versatile plant with the capability to morph from small patch to bush to vigorous 20-foot vine clinging to the sides of trees.

Killingbeck knows of a stand in Jamestown where the shiny three-pronged leaf vegetation grows as freestanding plants with tree-like “trunks” 4 inches in diameter.

“It’s impressive,” Killingbeck said the other day standing beside some of the freestanding ivy.

Whether these sturdy plants become the poison ivy of the future “is an open question.”

Deb Rosen, an associate dean of business administration at URI, says the poison ivy in her backyard certainly seems more vigorous and potent than in previous years.

“I was pouring alcohol on my arms and my back and it still hasn’t gone totally away and it’s been at least a month. It’s subsiding but I was kind of surprised how long I kept getting new patches.”

Rosen says she kept her distance from her poison ivy and routinely washed her hands when she came in. The likely culprit, or culprits, in her case were likely her two golden retrievers, she believes. They probably had the poison ivy oil on their fur and passed it on to her.

“They are going to the kennel to be cleaned,” she said. Safety tips

•Keep away from it. Although poison ivy loves the edges of trails and woods, it does grow just about anywhere. The old maxim “Leaves of three, let it be” is a good one to follow.

•Wash exposed skin as soon as possible. Urushiol is usually absorbed into the skin within 15 to 20 minutes. The rash and its uncontrollable itching can

appear within 8 to 48 hours afterward.

•Treatment: Calamine lotion will dry out the rash and stop it from spreading. In serious cases where the itching can also cause a secondary

infection, an oral steroid can

be prescribed.

tmooney@projo.com