Once you've had chickenpox, the virus that caused it remains in your body for the rest of your life. As you grow older, the virus can reactivate. Sometimes this occurs when your body is stressed — because of another infection or due to medications that suppress your immune system, for example. The result is shingles. Because you have some immunity against the virus, rather than getting a full body rash, the rash occurs in areas of skin supplied by the nerve where the virus is reactivated.

Postherpetic neuralgia occurs if your nerve fibers are damaged during an outbreak of shingles. Damaged fibers aren't able to send messages from your skin to your brain as they normally do. Instead, the messages become confused and exaggerated, causing chronic, often excruciating pain that may persist for months — or even years.

Shingles

Nov. 13, 2012