Poison ivy, poison oak, and poison sumac are plants that cause a rash in those allergic to them. This rash is caused by a chemical in the sap. About 50%-70% of people are sensitized to this chemical and are, therefore, allergic. Virtually everyone will eventually become sensitized if repeatedly exposed.
The allergic reactions to poison ivy, oak, and sumac occur when sensitized people come in contact with urushiol oil. This oil is found in the roots, stems, leaves, and fruit of the plant. This oil is released if the plant is damaged or bruised.
If not washed, oil from these plants may stay potent for years on clothing, tools, toys, and other items, especially in dry conditions.
Sensitized people are at risk if they:
Work or play in wooded areas during the spring, summer, and fall
Touch pets or animals that have come in contact with these plants
Handle clothes or objects that have come in contact with these plants
Are exposed to the smoke of these plants if they are burned
The main symptom of poison oak, ivy, or sumac is an intensely itchy, red rash. The rash appears within 24-72 hours of exposure to the oil. The rash often appears streaked and may develop into oozing blisters. The oozing material will not sensitize others.
The skin rash may cause discomfort. It is not serious, though, and usually resolves on its own in 1-2 weeks. However, you should contact a doctor right away if you are highly sensitive or have the following symptoms:
Swelling of the face or throat
Rash on the genitals
Swelling or rash that covers more than one–third of your body
Rapidly spreading rash
Signs of a bacterial infection, such as pain, increased redness, fever, or pus
Diagnosis of poison ivy, oak, or sumac is based on the presence of a characteristic itchy rash and possible exposure to plants containing urushiol oil.
If you have been exposed to poison ivy, oak, or sumac, wash your entire body right away. You can reduce your chance of getting a rash if you wash thoroughly with soap and water within 10-15 minutes of exposure. Using alcohol and water, wash all clothes, tools, and shoes that were in contact with the plant. One small study shows that cleaning with the oil-removing compound “Goop” or the poison-ivy prevention substance “Tecnu” is more effective than using soap alone. All 3 treatments reduced the occurrence of skin rash by more than 50% following contact.
If Rash Develops:
If a rash develops, the itching and blisters will usually disappear in 7-14 days without treatment. Treatment to reduce discomfort includes:
Outsmarting poison ivy and its cousins. US Food & Drug Administration website. Available at: https://www.fda.gov/ForConsumers/ConsumerUpdates/ucm049342.htm. Updated June 6, 2017. Accessed October 2, 2017.
Stibich AS, Yagan M, Sharma V, Herndon B, Montgomery C. Cost-effective post-exposure prevention of poison ivy dermatitis. Int J Dermatol. 2000;39(7):515-518.
Last reviewed September 2018 by
EBSCO Medical Review Board
Marcin Chwistek, MD
Last Updated: 9/17/2014
EBSCO Information Services is fully accredited by URAC. URAC is an independent, nonprofit health care accrediting organization dedicated to promoting health care quality through accreditation, certification and commendation.
This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.
To send comments or feedback to our Editorial Team regarding the content please email us at firstname.lastname@example.org. Our Health Library Support team will respond to your email request within 2 business days.