Poison ivy cases on the rise

An outdoorsman and hunter, Brian Medlin has stalked razor-tusked hogs, sharp-clawed bears and big deer while rambling through the woods of South Carolina.

But none of those creatures scares him like poison ivy, and its cousin, poison oak. Last year, Medlin’s eye swelled shut and his face broke out in an itchy rash after he touched a toxic vine while preparing to hunt deer. It was a miserable experience Medlin fears he could have to deal with again.

“Poison ivy and poison oak are in places that used to not have it,’’ said Medlin, a Pickens resident who heads the S.C. Bear Hunters and Houndsmen Association. “Our yard never had it, then all of a sudden last summer, it was all over the place.’’

Medlin isn’t the only person who has noticed an increase in toxic plants.

As carbon dioxide levels rise and the earth’s climate changes, the number of patients seeking treatment for exposure to poison ivy and other poisonous plants has nearly doubled at the Medical University of South Carolina since 2013.

By Sept. 1 of last year, MUSC had seen 335 patients with toxic plant-related outbreaks, compared to 173 in 2013, according to data compiled for The State newspaper by MUSC. And those don’t include mild cases, university officials said.

“Anyone who comes through our doors has it pretty bad,’’ MUSC dermatologist Dirk Elston said, noting that many patients have palm-sized blisters, oozing rashes and swollen eyes. “The worst one I’ve seen is someone who took a chainsaw to a tree who was covered with poison ivy. This person had really widespread, horrible dermatitis.’’

It’s hard to say whether the increase in poison ivy cases at MUSC, a regional medical center in the Lowcountry, represents a widespread trend in South Carolina, since the state Department of Health and Environmental Control doesn’t keep statistics on poison ivy cases. It’s also possible that the increase in cases is because more people are relying on MUSC for medical services.

But nationally, emergency room visits for poison ivy and skin rashes rose over a 10-year period ending in 2012, according to the U.S. Centers for Disease Control and Prevention. The CDC reports 472,000 visits to the emergency room as a result of poison ivy or skin rash in 2002, compared to 929,290 in 2012, according to statistics released last year.

While MUSC officials couldn’t explain the increase in poison ivy cases, scientific research indicates that higher carbon levels in the atmosphere may be fueling the growth of poison ivy.

Scientist Bruce Allen, a former Savannah River Ecology Lab researcher who has studied poison ivy vines, said it’s not surprising that more people would report medical problems.

The plant is on the rise and becoming nastier, he said. One widely cited study from 2006 found that poison ivy exposed to high carbon dioxide levels grew faster and the oil that causes itching became more toxic.

The six-year study, conducted through Duke University, found that carbon dioxide caused an average annual 149 percent increase in the growth of poison ivy. Other plants did not grow nearly as fast when exposed to elevated carbon levels, according to the study.

“Both the warmer climate and the direct effects of atmospheric carbon dioxide concentrations, not only benefits poison ivy growth, but the higher CO2 makes it more allergenic to people,’’ said Jacqueline Mohan, a University of Georgia researcher who led the Duke study.

Carbon dioxide has risen dramatically in the atmosphere since the Industrial Revolution and is a major cause of climate change. Carbon levels have now reached more than 400 parts per million, compared to about 280 parts per million before the Industrial Revolution of the 1800s, according to the National Oceanic and Atmospheric Administration. Emissions from factories and power plants are major contributors to increased carbon.

All that carbon might be the reason poison ivy vines are so big and dense at Congaree National Park, research shows. A 2007 study, conducted by Allen while working with Ohio State University, documented a 10-fold increase over 20 years in the number of vines at the park and in a forest along the Savannah River.

“Probably the most likely reason for that is increased levels of carbon dioxide,’’ Allen said.

Today, some poison ivy vines at Congaree National Park are as thick as a person’s wrist and climb high into the canopy of old growth trees. Distinguishing the poison ivy vines from other types of vines is relatively easy. They have strands of plant material resembling hairs extending from their bark. The ivy leaves come in clusters of three and are dark green. Poison ivy is native to South Carolina.

Park ranger David Shelley said poison ivy can thrive almost solely on carbon dioxide as a source of nutrients.

“Poison ivy is one of the few plants that responds this favorably to just CO2,’’ he said. “A lot of other plants, things like corn and wheat, actually need other nutrients like phosphorous and nitrogen, in proportion to CO2, to show a growth response.’’

Some researchers predict an increasing growth of poison ivy as carbon levels continue to rise and the earth’s climate warms.

That’s bad news for people like Medlin.

He said last fall’s bout with poison ivy or poison oak was only the most recent trouble he’s had with toxic plants. He usually gets about one case a year, often in the fall. Last year, it took him several days and the use of medicine to reduce the swelling in his eye.

“It just spreads like wildfire,’’ he said. “I always have to go get shots for this. It is so miserable.’’