Poison ivy is a common cause of a skin irritation called contact dermatitis that may result in a red, itchy rash consisting of small bumps, blisters or swelling.
Most people have some level of sensitivity to poison ivy and similar toxic plants, such as poison oak and poison sumac. The irritating substance is the same for each plant, an oily resin called urushiol (u-ROO she-ol).
Rashes caused by poison ivy and its cousins generally aren’t serious, but they certainly can be bothersome. Treatment for poison ivy mostly consists of self-care methods to relieve the itching until the reaction goes away.
Signs and symptoms of a poison ivy rash include:
Often, the rash has a linear appearance because of the way the plant brushes against your skin. But if you come into contact with a piece of clothing or pet fur that has urushiol on it, the rash may be more spread out.
The reaction usually develops 12 to 48 hours after exposure and can last up to three weeks. In severe cases, new areas of rash may break out several days or more after initial exposure. This may seem like the rash is spreading. But it’s more likely due to the rate at which your skin absorbed the urushiol.
Your skin must come in direct contact with the oil from the plant in order to be affected. Spreading blister fluid from scratching doesn’t spread the rash, but germs under your fingernails may cause a secondary infection.
Poison ivy, poison oak and poison sumac can all cause contact dermatitis and the resulting itchy rash.
- Poison ivy is a common weed-like plant that may grow as a bush, plant or thick, tree climbing vine. The leaves typically grow three leaflets to a stem. The leaves vary greatly in their shape, color and texture. Some leaves are shiny, smooth and elliptical. Others are elongated and toothed with distinct leaflets. In the fall, the leaves may turn yellow, orange or red. Poison ivy can produce small, greenish flowers and green or off-white berries.
- Poison oak can grow as a low plant or bush, and its leaves resemble oak leaves. Like poison ivy, poison oak typically grows three leaflets to a stem.
- Poison sumac may be a bush or a small tree. It has two rows of leaflets on each stem and a leaflet at the tip. The smooth edges of its leaves distinguish it from its harmless sumac relatives.
The irritating substance is the same for each plant, an oily resin called urushiol. When your skin touches the leaves of the plant, it may absorb some of the urushiol made by the plant. It takes only a tiny amount of urushiol to cause a reaction. Urushiol is very sticky and doesn’t dry, so it easily attaches to your skin, clothing, tools, equipment or your pet’s fur.
You can get a poison ivy reaction if you:
- Directly touch the leaves, stem, roots or berries of the plant, shrub or vine.
- Unknowingly rub the urushiol onto other areas of your skin. For example, if you walk through some poison ivy then later touch your shoes, you may get some urushiol on your hands, which you may then transfer to your face by touching or rubbing.
- Touch urushiol left on an item, such as clothing, firewood or even a pet’s fur (animals usually aren’t affected by urushiol). Urushiol can remain allergenic for years, especially if kept in a dry environment. So if you put away a contaminated jacket without washing it and take it out a year later, the oil on the jacket may still cause a reaction.
- Burn the plants and inhale the smoke. Even the smoke from burned poison ivy, poison oak and poison sumac contains the oil and can irritate or injure your eyes or nasal passages.
A poison ivy rash itself isn’t contagious. Blister fluid doesn’t contain urushiol and won’t spread the rash. In addition, you can’t get poison ivy from another person unless you’ve had contact with urushiol on that person.
Poison ivy rash typically goes away on its own within one to three weeks. In the meantime, you can use self-care methods and over-the-counter medications to relieve signs and symptoms. If the rash is widespread or results in a large number of blisters, your doctor may prescribe an oral corticosteroid, such as prednisone.
Scratching a poison ivy rash with dirty fingernails may cause a secondary bacterial infection. This might cause pus to start oozing from the blisters. See your doctor if this happens. Treatment for a secondary infection is generally with antibiotics.
The advice “Leaves of three, let them be” is familiar to many people, with good reason. It’s a reminder to stay away from plants that feature three leaflets to a stem, such as poison ivy.
The best way to prevent an allergic reaction is to identify and avoid contact with poison ivy and other poisonous plants. These suggestions may help:
- Identify poison ivy, poison oak and poison sumac. Learn what the plants and leaves look like and where they’re commonly found so that you can avoid them.
- Take precautions outdoors. When hiking or engaging in other activities that might expose you to poison ivy, try to stay on cleared pathways. If camping, make sure you pitch your tent in an area free of poisonous plants. Keep pets from running through wooded areas so that urushiol doesn’t accidentally stick to their fur, which you then may touch.
- Remove poison ivy. In your backyard, you can use an herbicide to get rid of poison ivy or use heavy gloves to carefully pull it out of the ground. Note that even dead plants can cause a reaction. Afterward, remove and wash your gloves and hands thoroughly. Don’t burn poison ivy or related plants because the urushiol can be carried by the smoke and cause irritation or injury.
- Clean anything that may be contaminated. Wearing long pants, socks, shoes and gloves will help protect your skin, but be sure to wash your clothing promptly with detergent — in a washing machine, if possible — if you think you’ve come into contact with poison ivy. Handle contaminated clothes carefully so that you don’t transfer the urushiol to furniture, rugs or appliances.
In addition, wash any other contaminated items, such as outdoor gear, garden tools, jewelry, shoes and even shoelaces, as soon as possible. If you must wait to wash any contaminated items, seal them up in a plastic bag or container to avoid contamination of other items. Dry cleaning also will get rid of urushiol.
- Wash your skin with mild soap and water. Gently washing off the harmful resin from your skin within five to 10 minutes after exposure may help avert a reaction. After an hour or so, however, the urushiol has usually penetrated the skin and washing won’t necessarily prevent a reaction, but it may help reduce its severity. Be sure to wash under your fingernails.
- Apply a barrier cream. Appy an over-the-counter barrier skin cream containing bentoquatam to protect your skin. Bentoquatam absorbs urushiol and prevents or lessens your skin’s reaction to the oil.