Poison ivy, oak, and sumac are plants that commonly cause an allergic skin reaction. The result is most often an itchy, red rash with bumps or blisters.
The rash is caused by skin contact with the oils (resin) of certain plants. The oils usually enter the skin rapidly.
This is one of the most frequent causes of skin rash among children and adults who spend time outdoors.
The plant has three shiny green leaves and a red stem.
Poison ivy typically grows in the form of a vine, often along riverbanks. It can be found throughout the United States, except in the Southwest, Alaska, and Hawaii.
This plant grows in the form of a shrub and has three leaves similar to poison ivy. Poison oak is mostly found on the West Coast.
This plant grows as a woody shrub. Each stem contains 7 - 13 leaves arranged in pairs. Poison sumac grows abundantly along the Mississippi River.
AFTER CONTACT WITH THESE PLANTS
The rash does not spread by the fluid from the blisters. Therefore, once a person has washed the oil off the skin, the rash does not often spread from person to person.
The plant oils may remain for a long time on clothing, pets, tools, shoes, and other surfaces. Contact with these items can cause rashes in the future if they are not cleaned well.
Smoke from burning these plants can cause the same reaction.
Red, streaky, patchy rash where the plant touched the skin
Red bumps, which may form large, weeping blisters
The reaction can vary from mild to severe. In rare cases, the person with the rash needs to be treated in the hospital. The worst symptoms are often seen during days 4 to 7 after coming in contact with the plant. The rash may last for 1 to 3 weeks.
Wash the skin thoroughly with soap and warm water. Because the plant oil enters skin quickly, try to wash it off within 30 minutes.
Scrub under the fingernails with a brush to prevent the plant oil from spreading to other parts of the body.
Wash clothing and shoes with soap and hot water. The plant oils can linger on them.
Immediately bathe animals to remove the oils from their fur.
Body heat and sweating can aggravate the itching. Stay cool and apply cool compresses to your skin.
Calamine lotion and hydrocortisone cream can be applied to the skin to reduce itching and blistering.
Bathing in lukewarm water with an oatmeal bath product, available in drugstores, may soothe itchy skin. Aluminum acetate (Domeboro solution) soaks can help to dry the rash and reduce itching.
If creams, lotions, or bathing do not stop the itching, antihistamines may be helpful.
In severe cases, especially for a rash around the face or genitals, the health care provider may prescribe steroids, taken by mouth or given by injection.
Wash tools and other objects with a dilute bleach solution or rubbing alcohol.
Do NOT touch skin or clothing that still have the plant resins still on the surface.
Do NOT burn poison ivy, oak, or sumac to get rid of it. The resins can be spread via smoke and can cause severe reactions in people who are far downwind.
When to Contact a Medical Professional
Get emergency medical treatment right away if:
The person is suffering a severe allergic reaction, such as swelling or difficulty breathing, or has had a severe reaction in the past.
The person has been exposed to the smoke of a burning poison ivy, oak or sumac.
Call your provider if:
Itching is severe and cannot be controlled.
The rash affects your face, lips, eyes, or genitals.
The rash shows signs of infection, such as pus, yellow fluid leaking from blisters, odor, or increased tenderness.
Wear long sleeves, long pants, and socks when walking in areas where these plants may grow.
Apply skin products such as Ivy Block lotion beforehand to reduce the risk of a rash.
Other steps include:
Learn to identify poison ivy, oak, and sumac. Teach children to identify them as soon as they are able to learn about these plants.
Remove these plants if they grow near your home (but never burn them).
Be aware of plant resins carried by pets.
Wash skin, clothing and other items as soon as possible after you think you may have come in contact with the plant.
Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.