POISON IVY

            The two most definitive traits of poison ivy or poison oak are 1) 3 leaflets on each compund leaf and 2) a red coloration at the apex where the three leaves connect. Poison ivy can climb trees as a vine (usually attaching close to the trunk), look like a shrub, or be a single, simple plant. All parts of a poison ivy plant--leaves, stem, fruits, and roots--produce an oil that can cause skin irritation in some people. Any contact of the body 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 a case of poison ivy internally by inhaling oil droplets that become airborne in smoke when the plants are burned. Also, you can get poison ivy in the winter simply by touching the stem, even though the leaves are gone.

            Poison ivy has more facts, myths, and disagreements about its properties than most  plants. You do not spread poison ivy by scratching where it itches, despite what some people say. New blisters and irritated areas can appear more than a week after exposure to the oils, but these merely represent the normal lag time that can occur after initial contact. Also, you cannot give poison ivy to others, except by bringing them into contact with the oils that are on your own body or 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. One serious case of poison ivy was contracted by a wildlife 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.

            According to dermatologists, the oils from poison ivy cause a contact dermatitis (which means inflammation of the skin) that cannot be distinguished from one caused by numerous other contactants. Among the plants known to cause dermatitis that is superficially similar to that caused by poison ivy are black walnut trees, red cedar, and fresh okra. However, many people, possibly most, are not affected by them.

            The skin irritation--blisters, burning, itching--normally occurs 24 to 48 hours after contact with any part of a poison ivy plant, and expression of the ailment follows a bell-shaped curve. The most severe symptoms occur midway between a 2- to 24-day period. One treatment for relief of the symptoms of a severe case is a steroid, such as predisone. The steroid masks the symptoms even though the body's response to the irritation continues. Some dermatologists caution that some doctors treat with steroids for too short a period. Thus if your reaction is following a 24-day cycle and you take steroids for only seven days, the symptoms could reappear before the peak of irritation has been reached.

            Botanical field guides distinguish between poison ivy and poison oak. Subtle differences are noted, ones that do not really matter for recognition of the plants. Both have three leaves and produce the oils that make you itch. Some biologists claim that poison oak is more virulent than poison ivy.

Last review:  October 12, 2007