Shingles skin rash on a patient's chest. Vesicles (blisters, grey) erupting on the left-hand side of a patient's chest. This is due to infection by the herpes zoster virus, and the condition is called shingles. The herpes zoster virus is dormant after a chicken pox infection. When it reactivates, it damages the skin's nerves and causes blisters and severe pain. It can be treated with the antiviral drug acyclovir, which must be used early to reduce post-herpetic pain. Because the disease is neurological in origin, it is restricted to the dermatome (area of skin controlled by a nerve) of the nerve it has infected. This explains the small area of skin affected. Photographed in Africa.