, poison oak and poison sumac are all members of the same plant genus (Toxicodendron), and contact with each of these species can lead to the development of a rash. The rash itself is an allergic reaction (called contact dermatitis) to chemicals in these plants. This contact dermatitis is a clinical diagnosis to be made by your primary care physician
, meaning that a history and physical exam usually confirms the cause, and no other testing is done in support.
There are several clues which support a diagnosis of poison ivy, including the location and characteristics of the rash and a recent exposure to the outdoors. Classic cases of poison ivy involve streaks of red rashes (caused by a leaf sliding across the skin) in parts of the bodies unprotected by clothing (such as the ankles or arms). The rashes tend to be red, very itchy, and often have vesicles (small bumps containing clear fluid). Once the exposed areas of the body and other objects that came into contact with the plant are cleaned and washed, the rash cannot be spread. Even the fluid oozing from your rash is not contagious.
If you do have poison ivy, treatment is used for symptomatic relief. Typically this involves either calamine lotion or oatmeal baths for a soothing effect. For severe itching, oral antihistamines may provide some relief. For rashes of moderate severity, high-potency steroid creams may aid in healing; for very severe cases, your physician may choose to prescribe oral steroids.