What are poison ivy, oak, and sumac?
Poison ivy, oak, and sumac are plants that can cause a red, itchy rash called allergic contact dermatitis. It is the most common skin problem caused by contact with plants.
What causes a poison ivy, oak, or sumac rash?
The rash is caused by contact with a sticky oil called urushiol (say "yoo-ROO-shee-all") found in poison ivy, oak, or sumac. You can get the rash from:
- Touching or brushing against any part of these plants, including the leaves, stems, flowers, berries, and roots, even if the plant is dead.
- Touching anything that has come in contact with these plants, such as clothing, sporting gear, gardening tools, or pet fur.
The rash is only spread through the oil. You can't catch a rash from someone else by touching the blister fluid.
The rash is an allergic reaction to the oil. You become allergic to it through contact. After you have come in contact with these plants, your immune system may start to react to the oil as though it's a harmful substance.
What are the symptoms?
The usual symptoms of the rash are:
- Red streaks or general redness where the plant brushed against the skin.
- Small bumps or larger raised areas (hives).
- Blisters that may leak fluid.
Some people are very allergic to the oil. In these people, even a little bit of the oil may cause serious symptoms that need medical attention right away, such as:
- Trouble breathing.
- Swelling of the face, mouth, neck, or genitals. The eyelids may swell shut.
- Widespread, large blisters that ooze a lot of fluid.
The rash usually takes more than a week to show up the first time you have a reaction to the oil. It develops in a day or two on later contacts. The rash may form in new areas over several days, but you will only get a rash where the oil touched your skin.
The rash usually lasts about 10 days to 3 weeks. But it may last up to 6 weeks in more severe cases.
How is the rash diagnosed?
A doctor can usually diagnose the rash by looking at it and asking questions about:
- When you were exposed to the plant.
- How long it took the rash to develop.
- Other rashes you have had.
- Your outdoor activities, work, and hobbies.
How is it treated?
If you get a mild rash, you can take care of it at home.
- Apply a wet cloth, or soak the area in cool water.
- Use calamine lotion to help relieve itching.
- Try not to scratch the rash. Scratching could cause a skin infection.
Do not use the following medicines. They can cause allergy problems of their own:
- Antihistamines applied to the skin (topical), such as diphenhydramine (found in Benadryl cream, spray, or stick).
- Topical anesthetics that contain benzocaine (such as Lanacane).
- Topical antibiotics that contain neomycin (such as Neosporin).
See your doctor if the rash covers a large area of your body or your symptoms are severe. A doctor may prescribe a corticosteroid cream to help clear up the rash. A severe rash may be treated with corticosteroid pills or shots.
How can you prevent the rash from poison ivy, oak, and sumac?
If you think you have touched any of these plants:
- Wash your skin right away with plenty of water and mild soap (such as dishwashing soap) or rubbing alcohol. Rinse often, so that the soap or rubbing alcohol doesn't dry on the skin and make the rash worse.
- Use a brush to clean under your nails.
- You can also try an after-contact product, such as Tecnu Original Outdoor Skin Cleanser, to clean plant oil from your skin, clothing, or tools.
- Wash any clothing or other items that might have the oil on them. Do it right away.
The best way to prevent future rashes is to learn to identify these plants and avoid them.
When you can't avoid contact with the plants:
- Wear long pants, long sleeves, and closed shoes to help keep the oil from getting on your skin.
- Wear vinyl or leather gloves. Rubber (latex), cotton, or wool gloves offer no protection.
- Wash well or throw away anything that came into contact with the plants.
Experts say not to burn plants like poison ivy, oak, or sumac. When these plants burn, urushiol attaches to smoke particles. Exposure to the smoke can cause a rash on your skin. Breathing in the smoke can also hurt your lungs.
Primary Medical Reviewer William H. Blahd, Jr., MD, FACEP - Emergency Medicine
Anne C. Poinier, MD - Internal Medicine
Adam Husney, MD - Family Medicine
E. Gregory Thompson, MD - Internal Medicine
Martin J. Gabica, MD - Family Medicine
H. Michael O'Connor, MD, MMEd, FRCPC - Emergency Medicine
Current as ofOctober 5, 2017
Current as of: October 5, 2017
Author: Healthwise Staff
Medical Review: William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Anne C. Poinier, MD - Internal Medicine & Adam Husney, MD - Family Medicine & E. Gregory Thompson, MD - Internal Medicine & Martin J. Gabica, MD - Family Medicine & H. Michael O'Connor, MD, MMEd, FRCPC - Emergency Medicine