Shingles (also known as "herpes zoster") is the result of reactivation of the varicella virus in one of the spinal nerves. The virus travels down the nerve, producing large blisters localised in the area that the nerve supplies.
Shingles therefore, involves an area of skin which is served by one sensory nerve. This area of skin is known as a dermatome. The dermatomes that are commonly affected during a shingles attack are those on the chest, abdomen or face. Only one dermatome is affected in a particular individual at any one time.
While shingles can occur at any age, it usually occurs in the elderly, due to the immune system’s "memory" of the virus reducing over time. The immune system may not be able to effectively control the dormant virus. Anyone whose immune system is compromised also loses the ability to control this virus.
Immune control can be reduced by stress, poor diet, immune suppression due to chemotherapy treatment and in transplant patients or people with HIV infection.