My understanding is that untreated shingles, may result in nerve damage. In fact there is no guarantee that treatment may prevent damage in all patients.

The Herpes Zoster virus continues to live in the body, forever.
It can activate if the immune system keeping is dormant changes, as in Chemo, or infections like pneumonia. It uses l-arginine amino acid to replicate. So high unbalanced arginine is thought to provoke attacks.

It lives in the dorsal root ganglia along the spine.

My shingles came from the stress of working midnights. It took a year of this shift work to result. Hubby's came from a hornet sting. A week after the sting, he had a severe case of shingles.

I personally believe that some PN's and other chronic pain may be traced to viral activity in the dorsal root ganglia. My shingles area was activated by a muscle massage... I couldn't move for 3 days, my neck was so sore, and my arm! I did not get blisters that time, but boy, the pain was horrific!