Herpes zoster is an infectious disease that affects the nerves and skin, such as chickenpox, which is caused by the herpes zoster virus and is called herpes zoster because of the band-like distribution of the skin. The herpes zoster virus is contagious and can usually flare up when the body is immunocompromised, overstressed or has some underlying disease such as diabetes or tuberculosis. The rash of herpes zoster usually occurs on one side of the body and is characterized by clusters of blisters along the nerves that can cross the midline of the body, and severe pain, which can occur on the head, face, neck, chest, abdomen, and extremities.