n.
or herpes zoster
Acute viral skin and nerve infection.
Groups of small blisters appear along certain nerve segments, most often on the back, sometimes after a dull ache at the site; pain becomes more severe when the blisters break out. Caused by the same virus as chickenpox , it probably results from reactivation of seemingly inactive virus in a partially immune person. Spontaneous recovery from the infection usually occurs within two weeks, but neuralgia may last months or even years longer.