A poison ivy rash is a type of skin irritation called allergic contact dermatitis. Poison ivy rash is caused by a sensitivity to an irritant found in poison ivy and similar toxic plants, such as poison oak and poison sumac. Each of these plants contains an oily resin called urushiol (u-ROO-she-ol) that can irritate the skin and cause a rash.
Although the itching from a poison ivy rash can be quite bothersome, the good news is that a poison ivy rash or one caused by poison oak or poison sumac generally isn’t serious. Poison ivy rash treatment consists of self-care methods to relieve itching until the reaction disappears.
Signs and symptoms of a poison ivy rash include:
Often, the rash looks like a straight line because of the way the plant brushes against the 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 eight weeks. The severity of the rash is dependent on the amount of urushiol that gets on your skin.
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 plant’s oil to be affected. Blister fluid from scratching doesn’t spread the rash, but germs under your fingernails can cause a secondary bacterial infection.
When to see a doctor
See your doctor if any of the following occur:
- The reaction is severe or widespread.
- The rash affects sensitive areas of your body, such as your eyes, mouth or genitals.
- Blisters are oozing pus.
- You develop a fever greater than 100 F (37.8 C).
- The rash doesn’t get better within a few weeks.
Poison ivy, poison oak and poison sumac can all cause contact dermatitis and the resulting itchy rash.
- Poison ivy is an extremely 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. Some leaves have smooth edges, while others have a jagged, tooth-like appearance. 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 oak may have yellow-white berries.
- 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 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. Even a small amount of urushiol can cause a reaction. Urushiol is very sticky and doesn’t dry, so it easily attaches to your skin, clothing, tools, equipment or pet’s fur.
You can get a poison ivy reaction from:
- Direct touch. If you directly touch the leaves, stem, roots or berries of the plant, shrub or vine, you may have a reaction.
- Urushiol remaining on your skin. You may develop a poison ivy rash after unknowingly rubbing 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.
- Urushiol on objects. If you touch urushiol left on an item, such as clothing or firewood, you may have a reaction. Although animals usually aren’t affected by urushiol, if it’s on your pet’s fur and you touch your pet, you may develop a poison ivy rash. 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.
- Inhaling smoke from burning poison ivy, oak or sumac plants. 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 that’s still on that person or on his or her clothing.
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 generally includes antibiotics.