Herpes zoster is the medical name for shingles.
The virus can be reactivated when the body's immunity to the virus breaks down. This may happen due to normal aging, or the body's immune system may become weakened due to stress from illness, physical or emotional stress, fatigue, poor nutrition, certain medications, chemotherapy, radiation therapy, or other factors. Once reactivated, the virus travels along nerve fibers, usually settling in fairly isolated areas of skin on one side of the body. The infected area of the body usually has severe pain, itching, redness, numbness, and the development of a rash. The rash on the skin develops into small, fluid-filled blisters called vesicles.