Shingles (Herpes zoster)

Health and Nutrition > Diseases > H Reviewed by Dr Dan Rutherford, GP

What is shingles?

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.

What causes shingles?

After the chickenpox virus has been contracted, it travels from the skin along the nerve paths to the roots of the nerves where it becomes inactive. The chickenpox virus then 'hibernates'. When the virus is reactivated, it travels via the nerve paths to the skin. It is not known what factors trigger a reactivation of the virus. Shingles generally affects the elderly, but occasionally occurs in children who have had chickenpox within the first year of their lives and in people with an immune deficiency.

Shingles can be a sign of immunodeficiency, caused by HIV or chemotherapy, for example, but most people who get shingles have a normal immune system.

What are the symptoms?

- 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.

How can it be prevented?

People who have never had chickenpox can reduce the risk of getting the virus by avoiding contact with people with chickenpox and shingles. Shingles itself is not preventable.

How is it diagnosed?