This is a picture of herpes zoster (shingles) on the arm. Shingles are caused by the same virus that causes chickenpox. Outbreaks of shingles follow the distribution of nerves in the skin. This distribution pattern, seen here on the arm, follows a dermatome.
Update Date 3/5/2014
Updated by: David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.