Shingles is a painful rash caused by the Varicella zoster virus (Herpes varicellae), which is the virus that causes chickenpox . Shingles occurs in people who have had chickenpox and is a reactivation of the dormant virus. Shingles often occurs many years after the initial chickenpox infection. Shingles is contagious and may itself cause chickenpox. However, contact with a person with shingles or chickenpox cannot cause shingles.

• The first sign that a reactivation of the chickenpox virus is taking place is a burning sensation on the nerve paths along which the virus is travelling. Nerve paths typically form half-circles around the body. The pain and subsequent rash correspond to the position of the nerve paths and are almost always on one side of the body or face only.
• The rash is typically accompanied by a fever and enlarged lymph nodes.
• Two to three days after the pain has begun, a typical rash appears: small blisters on red, swollen skin. It resembles the type that is seen during an attack of chickenpox but covers a smaller area.
• The rash usually reaches its peak after three to five days. Then, the blisters burst and turn into sores, which gradually scab over. The scabs fall off after two to three weeks.
• In some people, the area where the rash was located becomes extremely painful after the scabs have gone and can last from a few weeks to several months. This highly unpleasant after-effect of shingles is called postherpetic neuralgia.