Shingles rash on a man's chest. Shingles (herpes zoster) is caused by the infection of sensory nerves with the Ivaricella-zoster i virus, which also causes chickenpox. The virus can remain dormant in the body for years after chickenpox, becoming active again if the immune system is weakened. It attacks nerves feeding the skin, causing a rash of small, painful blisters in a defined area. Damage to nerves can result in severe pain, persisting for months or even years after the blisters have disappeared. There is no effective cure, although the antiviral drug Iacyclovir i may reduce the severity of an attack if taken early.