Poison ivy, oak, and sumac are plants that commonly cause an allergic skin reaction. The result is typically an itching, red rash with bumps or blisters.
Poison ivy is one of the most frequent causes of skin rash among children and adults who spend time outdoors. The plant can be found throughout the United States, except in the Southwest, Alaska, and Hawaii. It has three shiny green leaves and a red stem. Poison ivy typically grows in the form of a vine, often along riverbanks.
Poison oak is primarily found on the West Coast. It grows in the form of a shrub and has three leaves similar to poison ivy.
Poison sumac grows abundantly along the Mississippi River. It grows as a woody shrub. Each stem contains 7 – 13 leaves arranged in pairs.
The rash is caused by skin contact with the oils (resin) of these plants. Smoke from burning these plants can cause the same reaction. The oils usually enter the skin rapidly. It is rarely spread from person to person.
The rash does not spread by the fluid from the blisters. Therefore, once a person has washed the oil completely off the skin, the rash is usually not contagious.
Keep in mind that the plant oils may remain for a long time on contaminated clothing, pets, tools, shoes, and other surfaces. These contaminated items can cause rashes in the future if they are not properly cleaned.
- 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 is admitted to a hospital. The worst symptoms are often seen during days 4 to 7. 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 resins.
- 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.
Call immediately for emergency medical assistance if
Call 911 or go to an emergency room if:
- Someone is suffering a severe allergic reaction, such as swelling or difficulty breathing, or has had a severe reaction in the past.
- Someone has been exposed to the smoke of a burning plant.
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.
- Skin products such as Ivy Block lotion can be applied beforehand to reduce the risk of a rash.
Other steps include:
- Learn to identify poison ivy, oak, and sumac. Teach your children to identify them as soon as they are able.
- Remove these plants if they grow near your home (but never burn them).
- Be aware of resins carried by pets.
- Wash as soon as possible after a suspected exposure.
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Cydulka RK, Garber B. Dermatologic presentations. In: Marx JA, ed. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 118.
Habif TP. Contact dermatitis and patch testing. In: Habif TP, ed. Clinical Dermatology. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 4.