About This Condition
Certain plants in the Toxicodendron (formerly Rhus) genus contain a potent resin called urushiol that, when it comes in contact with skin, can cause a severe allergic reaction in people who are sensitive to it—approximately 85% of the population, according to the American Academy of Dermatology.
Plants in this group include Western poison oak (Toxicodendron diversilobum), Atlantic poison oak (T. pubescens), poison ivy (T. radicans), and poison sumac (T. vernix).
The skin rash caused by the plant resin urushiol is a form of “contact dermatitis.” It is a red, swollen, blistering rash that is both painful and itchy. The blisters can become weepy, but the fluid from them does not spread the rash. Once developed, the rash is not contagious or spread by scratching. Scratching should nevertheless be discouraged to prevent the blisters from becoming infected. The rash can be severe but it is self-limiting, which means it will eventually resolve with no treatment. Most people seek treatment anyway for relief from the symptoms.
The contact dermatitis caused by exposure to poison oak or ivy may be prevented if the exposed area is thoroughly washed within the first five minutes following contact. Individuals with a rash can soothe inflamed skin with cool compresses made from gauze or thin cloths dipped in water. Clothing, pets, and other objects that have been exposed to plant oil should be washed to prevent re-exposure.