How does the shingles interact with the body to produce the symptoms?

Shingles is essentially the adult version of chicken pox. After you get chicken pox, the virus hides in your dorsal ganglia and wait. When the body gets immuno-compromised, the virus is sometimes re-released and infects the body.

The virus travels from the dorsal ganglia down nerves to specific locations and can branch off into different nerves. The symptoms are similar to chicken pox except there it deals with the nerves as well increasing the pain and hence severity.