Herpes zoster, or shingles, is caused by the same virus that causes chickenpox. After an episode of chickenpox, the virus becomes dormant in the body. Herpes zoster occurs as a result of the virus re-emerging after many years. The cause of the re-activation is usually unknown, but seems to be linked to aging, stress, or an impaired immune system. Often only one attack occurs, without recurrence. If an adult or child is exposed to the herpes zoster virus and has not had chickenpox as a child or received the chickenpox vaccine, a severe case of chickenpox may develop, rather than shingles. After infection with chickenpox, the virus resides in a non-active state in the nerve tracts that emerge from the spine. When it is re-activated, it spreads along the nerve tract, first causing pain or a burning sensation. The typical rash appears in 2 to 3 days, after the virus has reached the skin. It consists of red patches of skin with small blisters (vesicles) that look very similar to early chickenpox. The rash often increases over the next 3 to 5 days. Then, the blisters break, forming small ulcers that begin to dry and form crusts. The crusts fall off in 2 to 3 weeks, leaving behind pink healing skin. Lesions typically appear along a single dermatome (the body area served by a single spinal nerve) and are only on one side of the body (unilateral). The trunk is most often affected, showing a rectangular belt of rash from the spine around one side of the chest to the breastbone (sternum). Lesions may also occur on the neck or face, particularly along the trigeminal nerve in the face. The trigeminal has three branches that go to the forehead, the mid-face, and the lower face. Which branch is involved determines where on the face the skin lesions will be. Trigeminal nerve involvement may include lesions in the mouth or eye. Eye lesions may lead to permanent blindness if not treated with emergency medical care. Involvement of the facial nerve may cause Ramsay Hunt syndrome with facial paralysis, hearing loss, loss of taste in half of the tongue and skin lesions around the ear and ear canal. Shingles may, on occasion, involve the genitals or upper leg. Shingles may be complicated by a condition known as post-herpetic neuralgia. This is persistence of pain in the area where the shingles occurred that may last from months to years following the initial episode. This pain can be severe enough to be incapacitating. The elderly are at higher risk for this complication. Herpes zoster can be contagious through direct contact in an individual who has not had chickenpox, and therefore has no immunity. Herpes zoster may affect any age group, but it is much more common in adults over 60 years old, in children who had chickenpox before the age of one year, and in individuals whose immune system is weakened. The disorder is common, with about 600,000 to one million cases in the U.S. per year. Most commonly, an outbreak of shingles is localized and involves only one dermatome. Widespread or recurrent shingles may indicate an underlying problem with the immune system such as leukemia, Hodgkin's disease and other cancers, atopic dermatitis, HIV infection, or AIDS. People with suppressed immune systems due to organ transplant or treatment for cancer are also at risk. | 
General Dermatology, Internal Medicine
