Shingles is caused by the reactivation of the varicella-zoster virus, which is the virus that causes chickenpox (a highly infectious condition that most people have during childhood).
Chickenpox causes an itchy rash that blisters and then crusts over. See the Health A-Z topic on Chickenpox for more information about this condition.
After you have had chickenpox, the varicella-zoster virus lies dormant (inactive) inside your body. It can later be reactivated and cause shingles.
Reactivation
It is not known exactly how the varicella-zoster virus is reactivated, but it may be linked to having lowered immunity (protection).
Your immunity to illness and infection can become lowered if there is a problem with your immune system (the body’s natural defence system). This can happen as a result of:
- Being older. As you age, your immunity may also decrease. Shingles most commonly occurs in people who are over 80 years old.
- Physical and emotional stress. The chemicals that are released by your body when you are stressed can prevent your immune system from working properly (see the Health A-Z topic about Stress for more information).
- Having HIV and AIDS. People with HIV may be up to 25 times more likely to get shingles than the rest of the population.
- Recently having a bone marrow transplant (bone marrow is the spongy material in the centre of some bones). The conditioning that you receive before the transplant will weaken your immune system.
- Recently having an organ transplant. You may need to take medication to suppress your immune system so that your body accepts the donated organ. After a transplant, 25-45% of people may develop shingles.
