Urushiol is the toxic agent that produces a violent irritant to the skin. Urushiol is found on the leaves, stems and roots of poison oak, poison ivy and poison sumac. You can get the Urushiol on you by touching the plant or touching other things that may have come in contact with the plant. There have been cases of people contracting the irritant inhaling smoke from a fire in which these plants where burned.

Effects include light itching lasting as long as a week. Followed by inflammation and water blisters. Fever, enlarged glands and abscesses also may result.
For cases that have gone past the itching stage, you really should see a doctor.

As for treatments, it is best to contact a pharmacist or your doctor for treatments.

The best way to avoid these plants is to get familiar with how they look and where you find them. You can get books at the library or bookstores on the subject.