by Thomas E. Harris, MD
Fellow of the Academy of Wilderness Medicine
Urgent Care Physician at MediServe Walk-In Clinic
Do you think you may have a rash caused by poison ivy? When the skin comes in direct contact with an irritating or allergy-causing substance, contact dermatitis can develop. Exposure to poison ivy, poison oak, and poison sumac cause more cases of allergic contact dermatitis than all other plant families combined.
Poison ivy and poison oak are both found in the Ozarks; however, poison sumac is not.
People of all ethnicities and skin types are at risk for developing poison ivy dermatitis. The severity of the reaction decreases with age, especially in people who have had mild reactions in the past.
What causes Poison Ivy rashes?
Poison ivy, poison oak, and poison sumac plants contain a compound called urushiol, which is a light, colorless oil that is found in the fruit, leaves, stem, roots, and sap of the plant. When urushiol is exposed to air, it turns brown and then black; plant leaves develop small black spots.
There are several ways that you can be exposed to urushiol:
- By touching the sap or rubbing against the leaves of the toxic plant at any time of year
- By touching something that has urushiol on it, such as animal fur or garden tools
- By breathing in smoke when toxic plants are burned
- Ginkgo fruit and the skin of mangoes also contain urushiol and can produce symptoms similar to poison ivy dermatitis
Poison ivy dermatitis is not contagious and cannot be passed from person to person. However, urushiol can be carried under fingernails and on clothes. If another person comes in contact with the urushiol, he or she can develop poison ivy dermatitis. I’ve seen multiple cases where the spouse picked up the laundry and that contact caused the poison ivy dermatitis.
Poison Ivy Signs and Symptoms
After contact with urushiol, approximately 50 percent of people develop signs and symptoms of poison ivy dermatitis. The symptoms and severity differ from person to person. These symptoms usually develop within four hours to four days after exposure to the urushiol. The symptoms are worse within 1 to 14 days after touching the plant, but they can develop up to 21 days later if one has never been exposed to urushiol before.
The most common signs and symptoms of poison ivy dermatitis:
- Intense itching
- Skin swelling
- Skin redness
After the initial symptoms, allergic individuals develop fluid-filled blisters in a line or streak-like pattern. The blisters can occur at different times in different people; blisters can develop on the arms several days after blisters on the hands developed. This does not mean that the reaction is spreading from one area of the body to the other. The fluid that leaks from blisters does not spread the rash.
Poison ivy is usually diagnosed based upon how the skin looks. Further testing is not usually necessary.
At Home Treatments
Poison ivy dermatitis usually resolves within one to four weeks without treatment. Treatments that may help relieve the itching, soreness, and discomfort caused by poison ivy dermatitis include skin treatments that you can do at home.
- Adding oatmeal to a bath may help relieve itching.
- Applying cool wet compresses may reduce swelling and relieve itching.
- Applying calamine lotion to the rash.
- If you develop blisters that begin weeping fluid, astringents containing aluminum acetate Burow’s solution and Domeboro, may help to relieve the rash.
- Antihistamines do not help to relieve itching caused by poison ivy dermatitis and do not treat the rash. Some antihistamines make you sleepy while others do not. The ones that make you sleepy, eg, diphenhydramine (Benadryl) can help you to ignore the itch while sleeping.
Treatments to avoid: Do not use antihistamine creams or lotions, anesthetic creams containing benzocaine, or antibiotic creams containing neomycin or bacitracin to the skin. These creams or ointments could make the rash worse. Do not use bleach to cleanse rash from poison ivy. These areas are open wounds, and bleach is a harsh substance that can damage the skin and slow the healing process.
When to See the Doctor
If the Poison Ivy dermatitis and blisters become unbearable or spread to the groin or face, you may consider seeking treatment from a physician. There are several treatments your physician may recommend.
- Steroid creams – Steroid creams may be helpful if they are used during the first few days after symptoms develop. Low-potency steroid creams, such as 1% hydrocortisone (available in the United States without a prescription) are not usually helpful. A stronger prescription formula may be helpful if used early.
- Steroid medications and injections – If you develop severe symptoms or the rash covers a large area (especially on the face or genitals), a doctor may prescribe steroid pills (eg, prednisone) or injections to help relieve itching and swelling. Pills are usually given for 14 to 21 days, with the dosage slowly decreased over time.
- Antibiotics – Skin infections are a potential complication of poison ivy, especially if you scratch your skin. If you develop a skin infection because of poison ivy dermatitis, you may need antibiotics to treat the infection. Do not use over-the-counter topical antibiotic creams; many bacteria are resistant to them and they are one of the chief causes of allergic contact dermatitis not caused by plants.
Tips for Preventing Poison Ivy
The best way to prevent poison ivy dermatitis is to identify and avoid the plants that cause it. These plants can irritate the skin year round, even during the winter months, and they can still cause a reaction after dying.
- Know what poison ivy looks like and avoid it. “Leaves of three, let them be” is a phrase often used to identify plants that cause poison ivy dermatitis. Generally, poison ivy and poison oak have three leaflets per leaf with flowering branches on a single stem. The Arkansas Native Plant Society has a nice article on identification.
- Wear protective clothing, including long sleeves and pants, when working in areas where toxic plants may be found. Keep in mind that the resin and oils from the toxic plants can be carried on clothing, pets, and under fingernails.
- Wear heavy-duty vinyl gloves when doing yard work or gardening. The oils from toxic plants can seep through latex or rubber gloves.
- After coming in contact with poison ivy, remove any contaminated clothing and gently wash (do not scrub or rub) your skin and under your fingernails with mild soap and water as soon as possible. Washing within 10 minutes after exposure can reduce the likelihood and severity of symptoms; washing the skin after 30 minutes of exposure typically will not help.
- Creams and ointments that create a barrier between the skin and the urushiol oil may be somewhat effective for people who are frequently exposed to poison ivy. Bentoquatam (Ivy Block) is one type of barrier cream that may prevent poison ivy dermatitis. It must be reapplied every four hours and it leaves a clay residue on the skin.
- Avoid burning poisonous vegetation, which can disperse the plant particles in the smoke, irritate the skin, and cause poison ivy dermatitis.