It's a common plant found in most of the United States. One form grows low to the ground and looks like weeds growing from 6 to 30 inches high. The other is a "hairy" vine that grows up a tree. Both have stems with three leaves.

How does poison ivy cause a rash?

The plant contains an oil called urushiol (say: oo-roo-shee-ohl) that most people are allergic to. You can get it on your skin by:

• Touching the plant or clothing that has come in contact with it.

• Touching gardening tools that may have the oil on them.

• Touching pets that have been around poison ivy.

• Burning the poison ivy plant. The oil from the plant is carried in the smoke.

What is a poison ivy rash like?

The rash will usually appear 1 to 2 days after coming in contact with urushiol. Reddening and swelling will be followed by small blisters, and the rash will become very itchy. After about a week, the blisters dry up and the rash fades. In cases where the rash covers large parts of the body, it may last much longer.

How is poison ivy treated?

Urushiol can bond to your skin within minutes. If you think you've come in contact with poison ivy, wash the area with plain cool water as soon as possible. This may help remove some of the oil. Products that contain solvents such as mineral oil (brand names: Technu, Zanfel) also may help to remove urushiol. Because urushiol can remain active for a long time, be sure to wash your clothes, shoes, tools or anything else that may have touched the plant.

Over-the-counter medications can soothe itching:

• Hydrocortisone creams (brand name: Cortizone-10)

• Calamine lotion

• Antihistamine tablets (one brand name: Benadryl)

• Oatmeal baths

You should call your doctor if:

• You have fever over 100 degrees.

• The rash covers large areas of your body.

• The rash is in your eyes, mouth or on your genital area.

• There is pus coming from the blisters.

• The rash does not get better after a few days.