If you or someone in your household develop a skin rash, see your doctor. He or she may suspect chickenpox over the phone, especially if that person has not had the chickenpox vaccine or the chickenpox disease before, but it is important for the doctor to look at the skin rash. It also will help to know whether the patient has been exposed to someone with chickenpox, although this is not necessary to make the diagnosis. Special blood tests, such as the FAMA test (fluorescent antibody to membrane antigen) and the ELISA (enzyme-linked immunosorbent assay), are also available, but they do not need to be done in most patients. Sometimes your physician may scrape a chickenpox blister to examine under the microscope.