Shingles occurs when the virus that causes chickenpox starts up again in your body. After you get better from chickenpox, the virus ”sleeps” (is dormant) in your nerve roots. In some people, it stays dormant forever. In others, the virus “wakes up” when disease, stress, or aging weakens the immune system. It is not clear why this happens. But after the virus becomes active again, it can only cause shingles, not chickenpox.
