Can you catch poison ivy by touching someone who has it?

We ask the experts to settle common questions we've all wondered about.

QUESTION Can you catch poison ivy by touching someone who has it?

ANSWER Poison ivy is a woody vine well known for its ability to produce urushiol, an oily irritant that causes dermatitis - painful, itchy rashes and blisters of the skin. The plant grows all over North America, particularly in wooded areas such as parks and forests.

Poison ivy rashes are very common, particularly in the summer and fall seasons when leaves are enriched with urushiol. About 50 to 70 per cent of North American adults are sensitive to the oily irritant found in the plant.

There are many myths about poison ivy. One is that you can catch it by touching someone who has the rash.

People get poison ivy by coming into contact with the stems, roots, leaves or skin of the fruits of the poison ivy plant, which all contain urushiol. Vigorous activities such as weeding, bushwhacking and cross-country travelling can transfer the oily irritant onto the skin, causing a person to develop a rash. But the rash itself does not contain urushiol, so you cannot get poison ivy by touching someone who has it.

Typical symptoms of poison ivy include red, itchy eruptions of the skin, which occur within one or two days of exposure to the plant. However, these rashes can appear as soon as five hours or as long as 15 days after exposure.

Poison-ivy-induced dermatitis can be highly inconvenient, but it's usually not a serious condition. Treatment includes oatmeal baths, oral antihistamines, topical steroids and systemic steroids for widespread rashes.

If you're exposed to urushiol, it's best to use plain water to wash it off because soap can spread the oil around. Showering can also spread it all over the body, so wash the affected area separately.

While you can't catch poison ivy by touching someone who has it, you should always use precautions. Urushiol can linger on clothing and other exposed surfaces, such as garden tools and pet fur, so avoid contact with potentially contaminated surfaces until they have been washed with soap and water. Urushiol doesn't affect animals and inanimate objects the way it does humans, so it's okay to keep washing them with soap and water until the urushiol is completely gone.

Dr. Sanjay Siddha is a dermatologist at Toronto Western Hospital, one of the three hospitals that make up University Health Network.