Herpes zóster, commonly known as shingles, is a viral infection caused by the reactivation of the varicella-zoster virus, which also causes chickenpox. After a person recovers from chickenpox, the virus remains dormant in the nervous system and can reactivate later in life, often leading to a painful rash and blisters on one side of the body. The condition typically affects older adults or individuals with weakened immune systems. Symptoms may include burning or tingling sensations, followed by a red rash that develops into fluid-filled blisters. Early treatment with antiviral medications can help reduce the severity and duration of the symptoms.