Shingles rash on a patient's abdomen. Small groups of vesicles (grey) erupting from an abdominal area of skin in a patient from Africa. This is due to infection by the herpes zoster virus, and the condition is called shingles. The herpes zoster virus lies dormant after a chicken pox infection. When it reactivates, it damages the skin's nerves and causes vesicles (blisters) and severe pain. It can be treated with the antiviral drug acyclovir, which must be used early to reduce post-herpetic pain.