Shingles can appear unexpectedly, even in people who seem perfectly healthy. It is caused by the same virus responsible for chickenpox. After chickenpox clears, the virus does not leave the body. It remains inactive inside the nervous system and may return many years later.

The virus is more likely to reactivate when the immune system becomes weaker. Aging, prolonged stress, certain illnesses, and treatments that suppress immunity may increase the risk. Shingles is more common after age 50, but younger adults can develop it too.

The first warning sign is not always a rash. Pain, burning, tingling, itching, or unusual sensitivity may begin in one area several days earlier. A cluster of painful blisters often follows, usually forming a band on only one side of the body because the virus travels along a particular nerve.

Early medical attention can make an important difference. Antiviral treatment works best when started soon after the rash appears and may reduce the length and severity of the illness. Delayed treatment can increase the risk of postherpetic neuralgia, a persistent nerve pain that may continue long after the skin has healed.

Shingles itself is not passed directly from person to person. However, fluid from its blisters can give chickenpox to someone who has never had it or received the vaccine. Recognizing the early signs, avoiding contact with vulnerable people, and speaking with a healthcare professional promptly may help prevent serious and painful complications.