Shingles is caused by reactivation of the chickenpox virus. It often begins with burning, tingling or pain in one area, followed within days by a rash of small blisters, classically in a band on one side of the chest, abdomen, back or face. The rash does not usually cross the midline.
It is generally not dangerous but can be very painful, and early antiviral treatment from a doctor (ideally within the first few days of the rash) can reduce severity and the risk of lingering nerve pain. Shingles affecting the area around the eye, the tip of the nose, or causing facial weakness, severe headache or confusion needs urgent assessment.
The fluid in the blisters can pass chickenpox to people who have never had it or been vaccinated, so keep the rash covered and avoid contact with pregnant people, newborns and anyone with a weak immune system until it crusts over. See a doctor promptly if you suspect shingles. This is general information, not a diagnosis.