The diagnosis is almost always made by the highly typical clinical presentation. It must be remembered that any dermatome in the body may be involved. Shingles can present with vesicles confined to a dermatome on the face or the extremities. Shingles involving the penis and vulva can be particularly confusing. These may look like herpes simplex infection but careful inspection shows a unilateral distribution. An acute eruption presenting with vesicles and erosions on the vulva is herpes zoster unless proven otherwise.
Viral culture or polymerase chain reaction can be performed on vesical fluid. Serologic testing will show evidence of past or active infections but this test is not commonly ordered.