Shingles is a systemic immune system issue.
Shingles is caused by the Herpes Zoster virus, the same virus that causes chicken pox. So if you have ever had chicken pox, you could get shingles, no matter what your age. The virus lays dormant in nerve roots until "activated." Then it travels down the nerve to the skin, where it causes the watery rash. Activation can occur from a variety of ways; including a weakened immune system, stress, exposure to the sun, drug use.
Herpes zoster is related to Herpes simplex 1, the virus that generally causes cold sores and to Herpes simplex 2, which generally causes genital herpes. I say generally because the two may be interchanged from certain types of sexual activity .http://www.webmd.com/skin...c-overview
PS While in graduate school I studied and performed research on the gene regulation of HSV-1, specifically the regulation and action of Immediate-early gene product ICP27.