Poison Ivy, Oak & Sumac
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Poison ivy, oak, and sumac contain an oil called urushiol (you-ROO-shee-all). When this oil touches the skin, many people develop an allergic reaction that causes a rash.
There are three ways to get this rash:
- DIRECT CONTACT
Touching a plant that contains urushiol. - INDIRECT CONTACT
Urushiol can stick to almost anything. Touching a pet's fur, gardening tool, or sports equipment that contains urushiol can cause the rash. - AIRBORNE CONTACT
Burning these poisonous plants releases particles of urushiol into the air. These airborne particles can land on the skin.
RECOGNIZING THESE POISONOUS PLANTS
While the saying “leaves of three, beware of me” can help identify poison ivy and oak, a more accurate saying is “leaflets of three, beware of me.” Each leaf on poison ivy and poison oak has three smaller leaflets. The middle leaflet has a longer stalk than the two on the sides.
Poison sumac can be identified by its row of paired leaflets that contains an additional leaflet at the end. Often the leaves have spots that resemble blotches of black enamel paint. These spots are actually urushiol, which when exposed to air turn brownish black. Before urushiol is exposed to the air, it is colorless or pale yellow.
Poison ivy grows as vines or low shrubs. Poison oak, with its oak-like leaves, is a shrub. Poison sumac is a tall shrub or small tree. In the spring, poison ivy develops yellow-green flowers. Come early fall, the leaves on some of these poisonous plants turn yellow or red. The plants with berry-like fruit also can change. On the mature plants, the fruit often turns off-white.
While urushiol begins to penetrate the skin in minutes, the rash usually takes time to appear. Typically, 12 to 72 hours pass before the person experiences severe itching, redness, and swelling, followed by small or large blisters. When the rash develops after a plant touches the skin, streaks or lines often reveal where the plant brushed against the skin. The rash can appear on any part of the body. While it may seem to spread, this is actually a delayed reaction. The rash does not spread and is not contagious.
Poison Ivy
Grows as a vine in the East, Midwest and South. In the far Northern and Western United States, Canada and around the Great Lakes, it grows as a shrub. Each leaf has three leaflets.
Poison Oak
In the West, this plant may grow as a vine but usually is a shrub (pictured). In the East, it grows as a shrub. It has three leaflets to form its leaves.
Poison Sumac
Grows in standing water in peat bogs in the Northeast and Midwest and in swampy areas in parts of the Southeast. Each leaf has seven to thirteen leaflets.
Poison ivy reaction
DEVELOPING A RASH
The first time urushiol touches the skin, an allergic reaction seldom occurs. With repeat exposure, sensitivity to urushiol develops. Sensitivity varies from person to person. About 85 percent of people develop an allergic reaction when adequately exposed to poison ivy. Only about 15 percent seem to be resistant. While sensitivity to poison ivy tends to decline with age, people who reach adulthood without developing a sensitivity have a 50 percent chance of developing an allergic reaction to poison ivy, oak, and sumac. Children who have reacted usually find that their sensitivity decreases by young adulthood. People who were once allergic to poison ivy may even lose their sensitivity entirely later in life.
Prevention of Poison Ivy
Avoiding contact is best. Dermatologists recommend:
- Recognize and avoid these poisonous plants.
- Wear long pants, long sleeves, boots, and gloves when it is not possible to avoid these plants.
- Apply an over-the-counter skin-barrier product that contains bentoquatum before going outdoors. Bentoquatum helps prevent urushiol from penetrating the skin.
A typical case of Poision Ivy
Treatment
When an allergic reaction develops, the skin should be washed well with lukewarm water and soap. All clothing should be laundered, and everything else that may be contaminated with urushiol should be washed thoroughly. Urushiol can remain active for a long time.
For mild cases, cool showers and an over-the-counter product that eases itching can be effective. Oatmeal baths and baking-soda mixtures also can sooth the discomfort. When a severe reaction develops contact a dermatologist immediately, or go to an emergency room. Prescription medication may be needed to reduce the swelling and itch.
A dermatologist is a physician who specializes in treating the medical, surgical and cosmetic conditions of the skin, hair and nails. To learn more about poison ivy, oak & sumac, call toll free (888) 462-DERM (3376) to find a dermatologist in your area.
©2008 American Academy of Dermatology
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National Library of Dermatologic Teaching Slides
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