Shingles, also known as zoster or herpes zoster, is a viral disease characterized by a painful skin rash with blisters in a localized area. Typically the rash occurs in a single, wide stripe either on the left or right side of the body or face. Two to four days before the rash occurs there may be tingling or local pain in the area. Otherwise there are typically few symptoms though some may have fever, headache, or feel tired. The rash usually heals within two to four weeks; however, some people develop ongoing nerve pain which can last for months or years, a condition called postherpetic neuralgia. In those with poor immune function the rash may occur widely. If the rash involves the eye, vision loss may occur.Shingles is due to a reactivation of varicella zoster virus (VZV) within a person's body. The disease chickenpox is caused by the initial infection with VZV. Once chickenpox has resolved, the virus may remain inactive in nerve cells. When it reactivates, it travels from the nerve body to the endings in the skin, producing blisters. Risk factors for reactivation include old age, poor immune function, and having had chickenpox before 18 months of age. How the virus remains in the body or subsequently re-activates is not well understood. Exposure to the virus in the blisters can cause chickenpox in someone who has not had it, but will not trigger shingles. Diagnosis is typically based on a person's signs and symptoms. Varicella zoster virus is not the same as herpes simplex virus; however, they belong to the same family of viruses.The shingles vaccine reduces the risk of shingles by 50 to 90%, depending on the vaccine used. It also decreases rates of postherpetic neuralgia, and if shingles occurs, its severity. If shingles develops, antiviral medications such as aciclovir can reduce the severity and duration of disease if started within 72 hours of the appearance of the rash. Evidence does not show a significant effect of antivirals or steroids on rates of postherpetic neuralgia. Paracetamol, NSAIDs, or opioids may be used to help with the acute pain.It is estimated that about a third of people develop shingles at some point in their life. While more common among older people, children may also get the disease. The number of new cases per year ranges from 1.2–3.4 per 1,000 person-years among healthy individuals to 3.9–11.8 per 1,000 person-years among those older than 65 years of age. About half of those living to age 85 will have at least one attack, and less than 5% will have more than one attack. The disease has been recognized since ancient times.