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Poison Ivy: Rash, Treatment & Pictures

posion-ivy-100615-02
Credit: US. Fish and Wildlife Service

Poison ivy is a toxic plant (Toxicodendron radicans) that causes an itchy and sometimes painful rash in most people when they touch it. A clear liquid in the plant's sap, called urushiol, causes the irritation.

Description

Poison ivy has four characteristic signs:

  • Leaves grow in clusters or three
  • Has alternating leaves (spiral arrangement)
  • Plant has no thorns
  • Each three-leaf cluster has its on own stem

The almond-shaped leaves range in color from light green (young) to dark green (mature), but turn red, orange or yellow during the fall. Mature leaves are slightly shiny. Leaflets are typically about 3 to 12 centimeters (1.2 to 4.7 inches) long, but can be up to 30 cm (12 inches). The leaves have a smooth surface with few or no teeth on their edges.

poison ivy vine
This coarse, hairy growth on the trunk of a tree is a mature poison ivy vine. As indicated by the watch, the vine can easily grow to the size of a man's wrist. The "hairs" allow the vine to grab onto the bark and grow up to the tops of even tall trees. All parts of the vine contain urushiol, including the hairs. Using a chain saw to cut down such a tree produces flying poisonous sawdust.
Credit: New York Department of Transportation.

Where it's found

Poison ivy grows throughout North America — in all U.S. states east of the Rocky Mountains, the Canadian Maritime provinces, Quebec, Ontario, Manitoba and mountainous parts of Mexico. It also grows in Asia — in Japan, Taiwan, Russian islands and parts of China.

Poison ivy is very common in suburban parts of New England, the Mid-Atlantic and southeastern United States. Poison oak, a similar plant species, grows in western North America.

Poison ivy berries
Poison ivy berries are a pale green when first formed, lightening to white as they mature.
Credit: New York Department of Transportation.

The plant normally grows in woods, especially in places where sun shines through. It can also be found in rocky places or open fields.

Poison ivy flowers between May and June. Its yellowish-white or greenish-white flowers grow in clusters slightly above the leaves. The plant has a grayish-white, berry-like fruit that matures in August to November. Not a true ivy, poison ivy can grow as a trailing vine, a climbing vine or a shrub.

Physical effects

Skin contact with poison ivy's oils causes a red, streaky and patchy rash; extreme itching; and red bumps that can form blisters. The rash is not contagious, but the oils can remain on clothing, shoes and other objects for a long time if not cleaned, and can cause rashes in the future.

Poison ivy rash
The left elbow of a man displays a rash that had been caused when he brushed against a poison ivy plant.
Credit: CDC.

Treatment

People exposed to poison ivy should wash the skin thoroughly with soap and warm water, ideally within half an hour. They should use a brush to scrub underneath the fingernails to prevent spreading the plant oil, and wash clothing and shoes with soap and hot water. Tools and other objects should be washed with a dilute bleach solution or rubbing alcohol.

Heat and sweating can make itching worse, so the exposed person should stay cool and use cool compresses on their skin. Calamine lotion and hydrocortisone cream may be used to ease itching and blistering. A lukewarm bath with oatmeal bath products or aluminum acetate may help with itching. Antihistamines may also be used.

If the rash is severe, particularly around the face or genitals, a health care provider may prescribe steroids.

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Tanya Lewis, LiveScience Staff Writer

Tanya Lewis

Tanya joined the LiveScience staff in 2013. She received a graduate certificate in science communication from the University of California, Santa Cruz in 2012. Before that, she earned a bachelor's degree in biomedical engineering from Brown University. She has interned previously at Wired.com, Science News, Stanford Medical School, and the radio program Big Picture Science. To find out what her latest project is, you can follow Tanya on .
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