Shingles are caused by

Herpes zoster or shingles is a viral infection due to the reactivation of varicella zoster virus from its latent state in dorsal root ganglion. Caused by varicella zoster virus(Human Herpes Virus 3). The skin eruption is preceeded by pain or paresthesia in the dermatome 3- days before its appearance(pre hepatic neuralgia). This is followed by unilateral,grouped, monomorphous vesicles within the distribution of one to three dermatomes. The eruption is usually accompanied by dull, burning pain. Usually, thorasic, ophthalmic division of trigeminal nerve, cervical, and other spinal nerves are frequently involved. Ref Harrison 20th edition pg 1278