Shingles rash on a patient's back, which has ruptured and caused a further infection. Shingles (herpes zoster) is caused by the infection of sensory nerves with the varicella-zoster virus, which also causes chickenpox. It causes the outbreak of small blisters on the skin in the area supplied by the nerve. The blisters last around two weeks, and are followed by severe pain in the affected area due to nerve damage. Antiviral drugs such as acyclovir can help to prevent the pain if taken early in the attack. If the drug treatment is delayed, however, there is no treatment, although painkilling drugs may provide some relief.