Herpes simplex virus’s cousin, the varicella zoster virus (aka herpes zoster virus), causes shingles. Shingles is caused by the chickenpox virus that infected you as a child, and then went into hiding in nerve cells near your spinal cord, the dorsal root ganglion. This reappearance of the virus is characterized by blisters along a nerve’s path -- often a curved track on the face and trunk, but usually only on one side -- that follows the nerve on that side as it comes from the spine or central nervous system.
These blisters can be associated with longer-term residual pain that 30 to 50% of cases describe as the worst burning pain of their life. There are medications you can take to reduce the severity of cold sores and the number of outbreaks you have. You need a booster shot of antibodies (from the vaccine) to protect yourself from shingles before that virus reappears. The vaccine provides about 70% protection, and if you’re unlucky enough to have an outbreak, reduces consequent pain by about 50%, but it can still feel horrible.