Local Trails
Hike Ontario Fact Sheet
Poison Ivy: The Scourge of the Trail

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The summer of 2001 seems to have been a bumper year for poison ivy. Hikers are reporting it luxuriating on and beside trails all over the province. It can be a nasty problem for those who are unfortunate enough to be affected. The following information, from a variety of sources which are listed at the end of the article, should help hikers cope with a hazard which is ever-present.

Poison Ivy can be found throughout Southern Ontario and north to Cochrane and Kenora, although it is at its most abundant in the southern part of the province. It grows in deep woods, in the open and on rocks, in sandy areas, swamps, roadsides and even gardens. It can be found as a carpet of low-growing plants or scrambling like a vine up trees, posts and shrubs.

The characteristic three leaflets of the plant can be quite varied in form and colour. In spring the red-green or bronze-green leaflets hang limply; in summer the leaflets become firmer and spread out, and their colour changes to deep or bright green, sometimes with a glossy surface. In the fall the leaflets may turn orange or wine-red, or in shaded areas, just become mottled yellow or dull tan. Leaflets can have smooth or toothed margins or can be lobed.

In spring the plant produces clusters of small, greenish-white flowers which become small round berries in summer. After the leaves fall, the berries remain on bare stems.

Hikers should learn to recognize this plant in its various stages. An encounter can lead to minor discomfort or even to serious medical problems. Consult the web sites listed bellow for excellent photos. Hand books on wildflowers and shrubs can also be helpful. Best of all, hike with someone who can identify the plant and work at recognizing it.
The oil which causes the allergic reaction can be found in the root, stem, leaf, flower and fruit of the plant. Any bruising of any part of the plant can release the oil which may stick to skin, clothing, boots, rucksacks and pets. Wherever the oil is, it can contaminate skin which comes in contact with it for months after. Reaction can set in within four hours or may not appear for up to ten days.

Some people seem to have a high tolerance to poison ivy but most people who have contact with it eventually have a reaction. Unfortunately once you have developed an allergy to the plant you never lose your sensitivity.

If you have come into contact with poison ivy you must wash the affected parts with soap and water within 15 minutes. It takes only a short time for the oil to penetrate the skin. Soap is necessary to remove the oil. Lather repeatedly and rinse thoroughly between latherings. Clothing, boots (and laces!) and all equipment and pets contaminated with the oil should be washed thoroughly with soap and water. Be careful handling any contaminated item to avoid transferring the oil to your skin.

The first sign of the poison ivy rash is a light itching and a faint blush of the skin. The itching intensifies and small watery blisters may appear in a few hours or possibly days. In more severe cases the blisters burst to become irritating, oozing sores, which finally dry up forming scabs. The rash is not contagious and the fluid from the blisters does not spread it. Poison ivy rashes usually clear up on their own in up to four weeks, but severe reactions with associated pain and swelling respond to steroids taken by mouth and a cortisone cream can help the rash heal. A doctor must prescribe these.

Persons with milder cases of poison ivy can be made more comfortable with cold compresses of water, or a mixture of two to four tablespoons of white vinegar in two quarts of cool water for 15 minutes twice daily. Other suggestions for easing the discomfort are offered in the Ontario Ministry of Agriculture, Food and Rural Affairs' Factsheet cited below. A temporary field remedy suggested in “A Natural Remedy for Poison Ivy” is to swab the juice found in the stem of jewelweed on to the affected area. Take some jewelweed home with you for further treatments.

A wise hiker wears long pants in poison ivy country and keeps alert for the plant. Remember the old saying, “Leaflets three – Let it be.”

Hike Ontario thanks the following authors and publications for permission to quote from articles on poison ivy:

Dunin-Bell, Ola, MD, FRCSC. “Skin Deep.” Trail Talk (Oak Ridges Trail Association Quarterly), Summer, 2001: 16.

Kirk, Terry and Sparling, John. “A Natural Remedy for Poison Ivy.” The Ganaraska News, April-July, 2001: 17.

A very useful factsheet from which information for this article was also drawn was written by J. F. Alex, Professor Emeritus, Department of Environmental Biology, Ontario Agricultural College, University of Guelph.

Web sites with additional information and good photos to help with identification: