Poison ivy is a very common plant found in most parts of the United States. It has 2 forms. One form grows low to the ground. It is usually found in groups of many plants and looks like weeds growing from 6 inches 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.
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.
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:
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).
If you develop a poison ivy rash, it will go away on its own in 1 to 3 weeks. Several over-the-counter medications are available to relieve the itching, including:
Call your doctor if:
Written by familydoctor.org editorial staff