Poison ivy - oak - sumac rash
Poison ivy, oak, and sumac are plants that commonly cause an allergic skin reaction. This is also called an allergic contact dermatitis. The result is most often an itchy, red rash with bumps or blisters.
Poison oak rash on the arm. Several plants produce toxins that cause skin reaction. This is the appearance of poison oak dermatitis. Note the typical linear streaks produced either by scratching or brushing against the plant. (Image courtesy of the Centers for Disease Control and Prevention.)
This is a typical early appearance of a poison ivy rash, located on the knee. These early lesions consist of multiple small blisters (vesicles), often in a line where the skin has brushed against the poison ivy plant. The person may then spread the toxin to other areas of the body by scratching.
This is a typical early appearance of a poison ivy rash, located on the leg. These early lesions consist of multiple small blisters, often in a line where the skin has brushed against the poison ivy plant. The rash is caused by skin contact with the oily sap (resin) of these plants. The oily resin usually enters the skin rapidly, and is seldom transferred from person to person. The rash is not caused by the fluid from the blisters. Thus, once the person has washed the oil off the skin, the rash is usually not contagious.
A rash is an eruption of changes in color or texture of the skin.
Causes
The rash is caused by skin contact with the oils (resin) of certain plants. The oils most often enter the skin rapidly.
POISON IVY
- This is one of the most frequent causes of skin rash among children and adults who spend time outdoors.
- The plant has 3 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 much of the United States.
POISON OAK
This plant grows in the form of a shrub and has 3 leaves similar to poison ivy. Poison oak is mostly found on the West Coast.
POISON SUMAC
This plant grows as a woody shrub. Each stem contains 7 to 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.
Symptoms
Symptoms include:
- Extreme itching
- 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.
First Aid
First aid includes:
- 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
In case of an allergy:
- DO NOT touch skin or clothing that still have the plant resins 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 from 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 burning poison ivy, oak or sumac.
Contact 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.
Prevention
These steps can help you avoid contact:
- 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.
References
Dinulos JGH. Contact dermatitis and patch testing. In: Dinulos JGH, ed. Habif's Clinical Dermatology: A Color Guide in Diagnosis and Therapy. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 4.
Freeman EE, Paul S, Shofner JD, Kimball AB. Plant-induced dermatitis. In: Auerbach PS, Cushing TA, Harris NS, eds. Auerbach's Wilderness Medicine. 7th ed. Philadelphia, PA: Elsevier; 2017:chap 64.
Marco CA. Dermatologic presentations. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 107.
Version Info
Last reviewed on: 7/8/2023
Reviewed by: Linda J. Vorvick, MD, Clinical Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
