POISON IVY CAN CAUSE PROBLEMS YEAR-ROUND

by Whit Gibbons

August 7, 2016

Q: We have retired to a neighborhood where we expect to spend more time walking through woods. How do we avoid issues with poison ivy and poison oak, and what's the difference between them? Do you have to touch the leaves to get the blisters on your skin?

A: Poison ivy, which includes poison oak, is the classic outdoor pest of the plant variety. Most botanical field guides distinguish between the two, but the differences are subtle and do not really matter in identifying the plants.

They both have three leaves on each stem and a red coloration at the apex where the three leaves connect, and both produce oils that make you itch.

Some biologists claim that poison oak is more virulent than poison ivy; others say this has not been firmly documented.

Someone itching like crazy from exposure to either plant doesn't care that the other one might be more virulent.

Poison ivy can climb trees as a hairy-looking vine (usually attaching close to the trunk), look like a shrub or be a single, simple plant. All parts of the plant — leaves, stem, fruits and roots — produce oils that can cause skin irritation in some people.

Any bodily contact with the oils can cause a problem, whether from patting a dog that has just walked through poison ivy or touching clothes that have come in contact with the plant.

You can even get poison ivy internally by inhaling oil droplets that become airborne in smoke when the plants are burned.

You can also get poison ivy in the winter simply by touching the leafless stem or vine. I know of one young boy's outdoor experience gone bad after climbing around on an oak tree with help from a big vine that turned out to be poison ivy.

Nonetheless, after spending thousands of hours at a research ecology lab with people who spend time year-round in swamps, woods and streams where poison ivy is as common as a household word, few of us ever got a serious case.

Perhaps ecologists, hunters and wildlife managers who are in the woods a lot avoid the plant without being aware they are doing so. The same would be true of any nature enthusiast whose passion is being outdoors, whether it be looking at birds, collecting mushrooms or simply hiking.

Most people have no reaction when they casually brush against poison ivy, and many are not sensitive at all. Some people spend their lives around poison ivy without ever having a reaction.

The beliefs, myths and disputes about the properties of poison ivy are legion. Some truths: You do not spread poison ivy by scratching where it itches, despite what some people say. This misperception occurs in part because new blisters and irritated areas can appear more than a week after exposure to the oils. But these merely represent the lag time that can occur after initial contact.

Poison ivy is not contagious, and you cannot give it to someone else, except by bringing them into contact with the oils that are on your body or your clothes after encountering the plant.

Many forms of wildlife can eat poison ivy without being adversely affected. Dozens of kinds of birds including bobwhite quail eat the fruits, which are clusters of smooth, white berries that appear in late summer.

I know of a serious case of poison ivy contracted by a student who sorted through the stomach contents of a recently killed deer. Among the data he recorded for his research on the diet of deer was that they sometimes eat a lot of poison ivy leaves.

The oils produced by poison ivy that make us itch are not directed toward protecting the plant from humans. The fact that some people experience dermatitis from an encounter with the plant is purely incidental.

Learn to recognize poison ivy during your walks in the woods and enjoy the diversity of the natural world.

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