Poison Ivy

What is poison ivy?

Poison ivy is a very common plant found in most parts of the United States. It has two forms. One form grows low to the ground. It is usually found in groups of many plants and looks like weeds growing from 6 to 30 inches high. The other form is a "hairy" vine that grows up a tree. Both have stems with 3 leaves. You may have heard the old saying, "Leaflets three, let it be." This is because most people are allergic to poison ivy.

How does poison ivy cause a rash?

The poison ivy plant contains an oil called urushiol (say: oo-roo-shee-ohl). This oil "bonds" to skin when it comes in contact with it. Most people are allergic to it. If you are allergic to urushiol and you get it on your skin, you'll develop an itchy, red rash. You can get the oil on your skin by:
  • Touching the poison ivy plant
  • Touching any clothing, including shoes, that have come in contact with the plant.
  • Touching any gardening tools that may have the oil on it.
  • Touching any pets that have been around poison ivy and have gotten the oil on their hair.
  • Burning the poison ivy plant. The oil from the plant is carried in the smoke.

What is a poison ivy rash like?

A poison ivy rash will usually begin to appear 1 to 2 days after coming in contact with urushiol. The affected area will get red and swollen. A day or so later, small blisters will begin to form, and the rash will become very itchy. During this time, it's important to try to keep from scratching the blisters. Bacteria from under your fingernails can get into the blisters and cause an infection. After about a week, the blisters will start to dry up and the rash will start to go away. In severe cases, where the poison ivy 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 that you've come in contact with poison ivy, you need to wash the area with plain cool water as soon as possible. This may help to get some of the oil off your skin. Products that contain solvents such as mineral oil (brand names: Technu, Zanfel) also may help to remove urushiol from your skin. 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 (like camping, sporting, fishing or hunting gear).

Once a rash starts to develop, there are several over-the-counter medications you can use to relieve the itching, including:
  • 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

More Information

For more information talk to your doctor.


Written by familydoctor.org editorial staff.

American Academy of Family Physicians

Reviewed/Updated: 12/06
Created: 06/05