Poison ivy rash is caused by a sensitivity to an oily resin called urushiol (u-ROO-she-ol), which is found in the leaves, stems and roots of poison ivy, poison oak and poison sumac.
At least 50 percent of the people who come into contact with these plants develop an itchy rash. The most dangerous type of exposure occurs when the plant is burned and the smoke is inhaled, which can affect your lungs.
Mild cases of poison ivy rash require no medical treatment. For more severe or widespread rashes especially if it's on your face or genitals your doctor may suggest taking corticosteroid pills, such as prednisone, for a few weeks.
Symptoms
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 typically lasts two or three weeks.
The severity of the rash depends on the amount of urushiol that gets on your skin. A section of skin with more urushiol on it may develop a rash sooner. You can also transfer the oil to other parts of your body with your fingers.
Your skin must come in direct contact with the plant's oil to be affected. Blister fluid doesn't spread the rash.
Causes
Poison ivy rash is caused by an oily resin called urushiol found in the leaves, stems and roots of poison ivy, poison oak and poison sumac. Urushiol is very sticky, 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, you may have a reaction.
- Touching contaminated objects. If you walk through some poison ivy and 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. If the contaminated object isn't cleaned, the urushiol on it can still cause a skin reaction years later.
- Inhaling smoke from the burning plants. Even the smoke from burning poison ivy, poison oak and poison sumac contains the oil and can irritate or harm your nasal passages or lungs.
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.
