If you live in North America and venture beyond your front porch, you’re at risk of contracting poison ivy. Thankfully, by learning to recognize this dangerous plant, you can limit the likelihood of developing a nasty rash.
Staying out of parks and forests does not guarantee your safety. Although poison ivy grows in wooded areas throughout most of the United States and Canada, it also lurks in backyards, hedges, weed patches, and gardens. Don’t make the mistake of thinking it always appears as an ivy. The plant also grows as a climbing vine, a bush, or a ground cover. Well-established vines on trees may resemble old grape vines or small tree limbs.
In the spring the leaves may be light green or reddish. In the summer they turn a dark green, then to red, orange, or yellow in the fall. The green summer leaves may have a shiny or waxed appearance, which fades in autumn. Leafless plants are difficult to identify, but also contain the oil that causes the rash.
The edges of the leaves may be smooth or slightly jagged. The vine is sometimes hairy and has no thorns. From May to July tiny whitish flowers may adorn the plant, maturing to berry-like fruits by late summer.
The arrangement of leaflets is how poison ivy is usually 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 leaflets like mittens, will itch like the dickens.”
As for the rash, it can appear from a day to a week or so after exposure to the plant. Any rash that occurs within minutes to a few hours after exposure to a plant is very unlikely to be poison ivy (hence the medical name, delayed hypersensitivity reaction). (However, other types of allergic reactions may occur to any plant.) Generally speaking, it takes the human body 24 hours or more to respond to the urushiol oil which 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. On the arms and legs this is usually from being brushed by the plant. On the neck or face it commonly occurs from having the plant oil on the hands and then wiping another body part. Interestingly, the palm surface of the hands rarely develop the poison ivy rash. In fact, in 25 years of medicine I can’t remember seeing a case.
The next stage is that of small blisters, which may enlarge, depending on your degree of allergy and amount of exposure. Sometimes the blisters burst, but this does not cause poison ivy to spread. Once the oil is off your skin (after a shower) poison ivy cannot be transmitted. Sometimes it looks like the rash has been spread from one body part to another, but this is actually due to earlier contact with the plant. Some areas of skin simply take longer to develop the rash.
Burning poison ivy, even the dry leaves and vines, is especially inadvisable. The smoke can carry the oil to your face, your eyes, and your lungs, producing severe symptoms. This occurs commonly at camp fires and when burning brush. Eating poison ivy may cause your internal organs to swell, producing a potentially fatal reaction. (Of course, in decades of medicine, I’ve never seen a person who’s eaten poison ivy.)
Learn to recognize the plant, avoid anything that resembles poison ivy, and the odds of remaining rash- and itch-free are in your favor.
Copyright 2010 Cynthia J. Koelker, MD