Zoster is caused by the chickenpox virus (Varicella), which is in the Herpes family, but has nothing to do with STDs. Chickenpox causes a fever and itchy rash all over the body; it goes away on its own in a week, but the virus remains dormant (asleep, latent) in a nerve. Years later, it can reactivate and cause a painful rash in just one nerve, on just one side of the body.
The rash consists of blisters or just red splotches, running in a band-like area. On the chest it would be along a stripe anywhere from spine to breastbone; on the abdomen, from spine to center of abdomen; on arms & legs, in a stripe; on the back, or anywhere. However, for 1-2 days before the rash appears, there may just be weird pain.
Zoster of the 8th cranial nerve leaving the brain can cause ear pain, vertigo, hearing loss, tinnitus (ringing in the ear) [called “Herpes Zoster Oticus”], and/or facial weakness (see Bell’s Palsy). There may be telltale blisters on the ear or in the ear canal, though maybe not. Zoster of the 5th cranial nerve causes obvious blisters on one side of the face, but can be dangerous if it affects the eye. We worry about this if blisters are on the forehead, and especially the tip of the nose.
Treatment only helps in the first few days; otherwise, Zoster goes away on its own in a few weeks. Some older persons (usually >65) may wind up with ongoing chronic pain. Even though anyone can get Zoster, it’s more common after 50. For anyone younger, I suggest an HIV test, since Zoster is very common in HIV. It’s usually negative.
There’s a vaccine available now, usually given to people 60-years-old and over (you can get it if you’re 50). It’s well-recommended, to prevent the complication of chronic pain in older age.