西瓜视频

[Skip to Navigation]
Sign In
JAMA Patient Page
May 16, 2024

Poison Ivy, Poison Oak, and Poison Sumac

Author Affiliations
  • 1University of Michigan Health System, Ann Arbor
  • 2Deputy Editor, JAMA
JAMA. 2024;331(21):1872. doi:10.1001/jama.2023.26355

Poison ivy, poison oak, and poison sumac are plants that frequently cause allergic skin reactions.

How Poison Ivy, Poison Oak, and Poison Sumac Affect Skin

These 3 plants contain sap oil (urushiol) in their leaves, stems, and roots, which is released on contact and penetrates the skin to cause an itchy, red rash (allergic contact dermatitis). Once urushiol is on the skin, it can be spread to other areas of skin by touch. People can also come into contact with urushiol by petting an animal that has sap oil on its fur. Rarely, urushiol can spread to other people through contact with clothing or objects (such as garden tools or fishing equipment) that has urushiol on it.

Approximately half to three-quarters of the US adult population develops a contact dermatitis rash after contact with poison ivy, poison oak, and/or poison sumac. Each year, approximately 10 million to 50 million people in the US develop rash from exposure to these plants. People at highest risk are those who work outdoors, such as construction, forestry, and farm workers; landscapers; and firefighters.

How Does the Rash Look and When Does It Develop?

The rash caused by poison ivy, poison oak, and poison sumac is red and bumpy in appearance, often arranged in streaks, and is very itchy. In severe cases, fluid-filled blisters may develop. The rash typically appears 24 to 48 hours after contact in people who were exposed to one of these plants in the past, with peak severity 1 to 14 days later. The rash can take up to 3 weeks to develop in individuals with a first exposure to one of these plants. The rash caused by poison ivy, poison oak, and poison sumac typically resolves within 1 to 3 weeks.

What to Do After Exposure

After contact with one of these plants, the whole body should be washed with a mild soap as soon as possible, and a brush should be used to scrub under the nails to remove urushiol before it is absorbed. Clothes and other items that may have been exposed to the sap oil should also be washed with warm, soapy water. Because pets may carry urushiol on their coats, they should be bathed if contact with poison ivy, poison oak, or poison sumac is suspected.

Treatment of Skin Rash From Poison Ivy, Oak, and Sumac

Topical treatments to help decrease symptoms include wet compresses, calamine lotion, oatmeal baths, and astringents (such as aluminum acetate) to dry a weeping rash. Steroid skin creams may reduce itching and blistering. Oral or intramuscular steroids may be prescribed for patients with severe blistering; rash on the face, hands, or genitals; or involvement of more than 20% of the skin. Although antihistamines do not relieve itching caused by allergic contact dermatitis from poison ivy, poison oak, and poison sumac, they may improve symptoms by causing sedation.

How to Avoid Poison Ivy, Poison Oak, and Poison Sumac

The key to prevention is to identify and avoid contact with these plants. Poison ivy has 3 leaflets, poison oak has 3 to 5 leaflets, and poison sumac has 7 to 13 pointed leaves. If you are going into wooded or marshy areas, wear long sleeves, long pants, boots, and gloves. Barrier skin cream, such as lotion that contains bentoquatam, may provide additional protection.

Box Section Ref ID

For More Information

To find this and other JAMA Patient Pages, go to the Patient Information collection at .

The JAMA Patient Page is a public service of JAMA. The information and recommendations appearing on this page are appropriate in most instances, but they are not a substitute for medical diagnosis. For specific information concerning your personal medical condition, JAMA suggests that you consult your physician. This page may be downloaded or photocopied noncommercially by physicians and other health care professionals to share with patients. To purchase bulk reprints, email reprints@jamanetwork.com.
Back to top
Article Information

Published Online: May 16, 2024. doi:10.1001/jama.2023.26355

Conflict of Interest Disclosures: None reported.

Source: Kim Y, Flamm A, ElSohly MA, et al. Poison ivy, oak, and sumac dermatitis: what is known and what is new? Dermatitis. 2019;30(3):183-190.

×