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Shingles is a viral infection caused by the same virus that causes chickenpox – in fact you can only develop shingles if you have already had chicken pox at some point in your life.

The virus that causes chickenpox and shingles is the herpes zoster virus, and the medical term for shingles is 'herpes zoster'. This virus belongs to the herpes family of viruses which include the variants that cause cold sores and genital herpes (however having varicella-zoster does not expose you to the other types, or vice-versa).

Around one in three people who have not received the chickenpox vaccination and who have had chickenpox in the past, go on to develop shingles.


The direct cause of shingles is the reactivation of the virus in someone who has previously had chickenpox. The virus can lie dormant for many years in nerve cells close to the spine before becoming reactivated to cause shingles, which affects the nerves.

It is not fully understood what causes this reactivation of the virus, however a number of risk factors have been identified, including…

  • Age – shingles generally affects people over the age of 60 (although there is an increase in risk from the age of 40).
  • Stress (physical or emotional).
  • Immune system compromise - this may be due for example to organ or bone marrow transplant surgery, cancer treatment (e.g. chemotherapy or radiation therapy), HIV / AIDS.

People generally only have shingles once, however any form of immune system compromise may lead to multiple infections.


The main symptoms of shingles are…

  • Pain or a feeling of burning, tingling or numbness affecting a small area of skin on one side of the body (the pain can sometimes be quite severe).
  • Within 2-3 days the appearance of a red rash at the site of the pain, which develops into fluid-filled blisters (which then burst and form a crust).

Some people do not develop the rash at all.

In some cases, there may be other symptoms, such as…

  • Tiredness.
  • Headache.
  • Fever.
  • Heightened sensitivity to light.

Where the area affected is near the eye, there is a possibility of permanent damage to the eye, so if this is the case, you should seek immediate medical attention.

Anyone affected by additional symptoms such as a severe headache, memory loss, confusion or fever, should also seek immediate medical attention.

It is important to have shingles treated as soon as any of these symptoms appear, since if untreated, pain (and other symptoms) can last for a long time. This is called 'post-herpetic neuralgia'. In some cases, the rash and blisters can become infected.

Tests / Diagnosis

Shingles is relatively easily diagnosed simply by reviewing symptoms and seeing the rash/blisters. Your doctor may take a sample from the blisters to confirm the diagnosis.