You probably had chickenpox as a young child in primary school or earlier. The fever, blisters, and itching lasted for a week or so, depending on how serious your case was. Once the blisters dried, you were no longer considered contagious and were allowed to return to school.
Now we know that the varicella zoster virus that causes chickenpox never completely leaves your body, even after you return to perfect health. The virus is dormant, which means that it “goes undercover,” hiding or sleeping within the nerves beside your spinal cord. Years later, the virus particles can reactivate. They move outward along the nerve fibers until they reach the skin, at which point they cause the painful rash called shingles.
The shingles rash covers only a small area on your body, and is always confined to one side. The lines of blisters follow the nerve fibers that grow outward from the spinal nerve roots under the skin.
- If the virus particles were dormant in an area near the top part of your spinal cord, you may get blisters on your neck, face, head, mouth, eyes, or ears as they spread along the facial nerves.
- If they were dormant somewhere in the middle of your back, your rash will probably form a narrow “belt”-like band that starts at the spine and comes around one side of your body to the front of the chest or abdomen. Viruses that were dormant towards the bottom of your back may migrate down the nerves of your legs and into your feet, causing patterns of blisters in those areas of your body.
Only people who have had chickenpox at some earlier time in their life can develop shingles. Scientists do not yet understand why the viruses become active again after many years, but the following factors are known to increase your risk of developing the condition:
- Older age, especially being older than 60 years–the older you are, the higher the risk. This is the primary risk factor.
- A weakened immune system, which can be caused by cancer treatment (chemotherapy or radiation), infection with HIV, long-term use of steroid medications, or treatment to prevent rejection of an organ transplant.
- Extreme stress. Even a single stressful life event can weaken your immune system.
- Physical stress such as having a cold or sunburn.
- Your chickenpox infection occurred before you were one year old.
Last Updated July 2020