What begins often as a breezy stroll through nature can sometimes end in an insatiable itch, a rash of red dots and a mess of oozing blisters. Those who've needed treatment for a poison ivy rash are not likely to forget the experience and are forever on the lookout for the glossy, three-leafed plants that provoke an allergic reaction in about 85 per cent of the population.

In fact, new research suggests we should all be on our toes as the plant is growing like never before. According to a study published in the July 2007 issue of Weed Science, high levels of carbon dioxide linked to climate change is providing ideal growing conditions for poison ivy.

Researcher Lewis Ziska, an ecologist with the U.S. Department of Agriculture, found that when the plants were exposed to carbon dioxide levels matching current levels in the atmosphere, they grew at an accelerated pace — with larger, more robust leaves. The plants were also found to produce more potent compounds called urushiols that would raise the intensity of the allergic reaction.

The latest research follows an earlier study published in the June 2006 issue of the Proceedings of the National Academy of Sciences. The study, from researchers at the University of Duke in North Carolina, found that when they grew poison ivy plants in an atmosphere with high carbon dioxide levels, the plants grew twice as fast and produced more concentrated oil.

John Stinchcombe, an ecology and evolutionary biology professor at the University of Toronto, says the two studies indicate the plants are very responsive to climate change.

"The recent study suggests that poison ivy is itself very sensitive to very moderate changes in carbon dioxide such as ones that have been observed over the last 50 to 60 years," he said.

Stinchcombe warns that people will have to brace themselves for even more problems linked to climate change.

"I think with global climate change one of the potential consequences of it [might] be an increased abundance of either weedy species or species that are harmful to humans through allergies like poison ivy or maybe they're harmful to agriculture or they're harmful to clean waterways and so on," he said.

"There's a real potential for climate change to make our lives harder by increasing the abundance of species that cause problems for us."

Become more vigilant

With poison ivy poised to become even more prevalent, people will have to be more vigilant scouring their backyards, campsites and hiking trails for the vines. School children are often taught the following rhyme to help them spot the plant: "Leaves of three, let it be; berries white, danger in sight."

Hikers will have to adjust, depending on the season, as the leaves change colours from a reddish hue in spring to green in summer and a yellow, orange or red in the fall. In June and July, the plants have yellow flowers and in September they bear clusters of green and yellow berries.

Older plants will have leaves with lengths of up to 55 millimetres. Upright leafy stalks span heights of up to 80 centimetres while aerial vines can be as tall as 10 metres.

The plant, which grows in every province save Newfoundland and Labrador, thrives in sunny areas and in both sandy and rocky terrains. Poison ivy is also often found on the outskirts of forests.

Experts say people should be particularly cautious in the spring when the tender leaves can be broken quite easily. Hikers should also wear long clothing and stay on the trails.

Exposure to the oil will cause skin inflammation, known as Rhus-dermatitis. Symptoms include persistent itch, rashes, swelling, blisters and sometimes a high temperature and restlessness. Be sure to clean exposed areas with soap and cold water immediately to prevent the rash from spreading. Washing the skin an hour after exposure won't stop a reaction from occurring but may help ease swelling and itching.

Pet owners should also be mindful that the sticky oil can become caught in animal fur.

Pesticides vs. cultivation

Patches of poison ivy growing in residential backyards should be approached with care and caution, says Stephen Belliveau, a spokesman for Health Canada's Pest Management Regulatory Agency. Consumers can use a herbicide or dig up the weed, turning over the soil frequently to prevent the plant from regenerating.

"Some people prefer to use chemical control which avoids the person touching the plant and reduces the risk of getting the oil on the skin surface," Belliveau said. "But then there are a lot of people who don't want to use any herbicides at all and the option for them is to use cultivation to remove it."

People who do choose to dig up the weed should be sure to use rubber gloves and should also consider using disposable coveralls.

Belliveau also warns that if the plant is burned, toxins will be released in ash, smoke and dust particles.

"If someone were to inhale it they would end up with a severe reaction likely because it would be in the throat and the lungs," he said.

Some treatment

If you are suffering from inflammation, expect to be in discomfort for one to three weeks. To ease the itch, a patient may choose to soak in a tub filled with cool water.

If blisters weep pus, if the rash persists, or if new rashes develop in different areas, a doctor should be consulted for other treatments such as a corticosteroid cream, an antihistamine or antibiotics that will help ease symptoms.

Otherwise, over-the-counter treatments, including calamine lotion and skin washes, are also available.

Items of clothing exposed to poison ivy should be washed separately in hot, soapy water.

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