Bobby Marshall, age 14, of Rutland, Vt., for his question:

WHAT CAUSES SHINGLES?

Shingles cause burning pain in a rash of blebs that usually follows the nerve course. Shingles is caused by an infection of a nerve cell by a virus that is similar if not identical to the chicken pox virus.

Common sites of the rash and pain connected with it are the trigeminal nerve of the face and nerves of the torso.

Shingles is also called herpes zoster. A person who has recovered from chicken pox still carries the virus in a latent state in nerve cells along the spinal cord or in the brain. The virus can later be reactived, migrate to the skin and cause blisters along a band following a nerve, almost always on one side of the body. Affected people, especially those over 60, may develop associated pain. The pain can be servere and persist for weeks or even months.

There seems to be no cure for shingles although steroid medications sometimes bring relief. Pain relieving medications may be necessary. Cool compresses help dry up the blisters and prevent bacterial infection.

After the rash of chicken pox heals, the virus apparently is able to persist in nerve cells for many years and may reappear even decades later as shingles.