If you live in North America and venture beyond your porch, you are at risk of getting poison ivy. Fortunately, by learning to recognize this dangerous plant, you can limit the likelihood of developing a nasty skin rash.
Staying away from parks and forests does not guarantee your safety. Although poison ivy grows in wooded areas in most of the United States and Canada, it also lurks in backyards, hedges, patches of brush, and gardens. Don’t make the mistake of thinking that it always appears as an ivy. The plant also grows as a vine, shrub, or groundcover. Well-established vines on trees may resemble old vines or small tree branches.
In spring the leaves can be light green or reddish. In the summer they turn dark green, then red, orange, or yellow in the fall. Green summer leaves can have a shiny or waxy appearance, which fades in fall. Leafless plants are difficult to identify, but they also contain the oil that causes the rash.
Leaf edges may be smooth or slightly jagged. The vine is sometimes hairy and thornless. From May to July, small whitish flowers may grace the plant, maturing into berry-like fruits in late summer.
The leaflet arrangement is how poison ivy is often identified: clusters of three leaves, with the middle leaf on a slightly longer stem. Although other plants have a similar pattern, remember, “Leaves of three, let it be” and “Side leaves like mittens, sting like dickens.”
As for the rash, it can appear from a day to a week after exposure to the plant. Any rash that occurs within a few minutes to a few hours after exposure to a plant is highly unlikely to be poison ivy (hence the medical name, delayed hypersensitivity reaction). (However, other types of allergic reactions to any plant can occur.) Generally speaking, it takes 24 hours or more for the human body to respond to the urushiol oil that causes typical poison ivy.
The first sign of poison ivy dermatitis is usually erythema (redness) in the area of exposure. Clusters of red dots or streaks are typical. In the arms and legs this is usually due to the rubbing of the sole. On the neck or face, it commonly occurs from getting the vegetable oil on your hands and then cleaning another part of the body. Interestingly, the surface of the palm of the hands rarely develops the poison ivy rash. In fact, in 25 years of medicine I don’t recall seeing a case.
The next stage is that of small blisters, which can become larger, depending on the degree of allergy and the amount of exposure. Sometimes the blisters burst, but this does not cause poison ivy to spread. Once the oil is removed from the skin (after a shower), poison ivy cannot be spread. Sometimes it appears that the rash has spread from one part of the body to another, but this is actually due to previous contact with the plant. Some areas of skin simply take longer to develop the rash.
Burning poison ivy, including dead leaves and vines, is especially inadvisable. Smoke can carry oil into the face, eyes, and lungs, producing severe symptoms. This commonly occurs in campfires and when weeds are burned. Eating poison ivy can cause your internal organs to swell, producing a potentially fatal reaction. (Of course, in decades of medicine, I have never seen a person eat poison ivy.)
Learn to recognize the plant, avoid anything resembling poison ivy, and the odds of staying rash and itch-free are in your favor.
Copyright 2010 Cynthia J. Koelker, MD
