Poison Ivy Is a Rash Experience

It was a most enjoyable trip to the cottage to meet her future husband’s parents. But as he drove her back to the city, she felt nature calling. Obligingly, he pulled over alongside a convenient thick wood into which she excused herself for a few moments. It wasn’t until several hours later the dreadful truth emerged. The wood had been full of poison ivy. There followed several weeks of itchy embarrassment.

---

By far the number of dermatitis cases experienced by Canadians every year involves Toxicodendron radicans. Growing in every province except Newfoundland, it is particularly abundant in southern Ontario and Quebec, although it may be encountered surprisingly far north in Ontario’s Cochrane and Kenora regions. Thanks to increased levels of atmospheric carbon dioxide, it is flourishing as never before throughout its range (Science News, June 2006). Almost everything about the plant is variable including its former listing as Rhus radicans. It may grow as a dense groundcover, a shrub or even a vigorous vine scrambling over trees, poles and fences. The flowers are usually greenish-white but may be cream and even yellow. The berries that follow in clusters are white, or possibly grey, green, even yellowish. One thing won’t vary: the leaves. These are compound in form, consisting of three glossy leaflets, pinkish as they emerge, turning green and in fall red, orange or yellow. The old warning is excellent: leaflets three, let it be.

---

---

While by law designated an obnoxious weed, this does not prevent it from occurring anywhere and everywhere, spread by more than 60 species of birds that relish the fruits. The seeds pass through their systems unharmed, to be deposited with a good dollop of fertilizer further away. Once well established the resulting plant is difficult to eradicate. The problem has been made worse by banning in recent years of chemical herbicides for home use, the only truly effective answer. Cut back, the roots are known to survive for years. Even if dug out, the tiniest piece left behind is capable of re-emerging to afflict another day. Merely brushing against the plant is enough to raise a rash, if nothing worse. So may patting a pet that has run through a patch but will remain unaffected. Inhaling the smoke from burning plants is even more deadly as it will affect the lungs. Even century-old specimens can continue to cause dermatitis. The toxicity is caused by urushiol, an oily allergen. The first indication of infection will be a violent itch, followed perhaps by inflammation, blisters and even oozing sores. The effects last for weeks and, in serious cases, months. Those spending time outdoors, including gardeners, hikers and backpackers, should carry a bottle of rubbing alcohol with them as a precaution. This is reliable for wiping off the urushiol. Cold water is less so, and never try hot water – it opens the pores of the skin, increasing infection. Soap may also have the same effect, moving the oily substance around. The first few moments following an encounter are the critical ones for removal. Some authorities suggest a time frame of as little as three minutes. How can you be sure you, your clothing, tools or equipment has become contaminated? Following a particularly virulent run-in with poison ivy’s west coast cousin poison oak, Rebecca Braslau of the University of California, Santa Cruz, has developed and patented a substance that fluoresces in the presence of urushiol to give an early warning, according to Arielle Duhime-Ross writing in the current edition of Scientific American. Impressive indeed until it is revealed that the sprayed area must be held up to a fluorescent light when the urushiol oils will glow blue. Where you find a fluorescent light within a few minutes when out in the bush, neither Ms. Braslau nor Ms. Duhime-Ross tells us. An extraordinary fortunate 15 per cent of Canadians are unaffected by close encounters of the poison ivy kind. But they may not remain so indefinitely. As with bee and wasp stings, at a second encounter, they too will experience an allergic reaction. The other 85 per cent of us may not only be allergic but, following dermatitis caused by poison ivy can become allergic to mangoes and cashews, which are also member of the family Anacardiaceae. It may pay to botanize.

---