People who have chickenpox---a viral infection of the skin---typically recover without complications, but the varicella-zoster virus that caused it remains dormant in the nerve fibres near the skin. The body's immune system, comprised mostly of white blood cells, keeps the virus in check. A compromised or debilitated immune system, known as leukopenia (low white blood cells in the blood), allows the development of a condition called shingles, where lesions erupt, usually around the trunk of the body.
The rash from shingles starts out as a tingling in the skin, followed by burning and discomfort. Red spots then develop, and finally turn into fluid-filled blisters, called vesicles. The rash is usually only present on one side of the body at a time.
Eye and Ear Symptoms
Because the virus travels through the nerves, it can causes eye and ear pain upon reactivation. When this happens, the rash is not necessarily visible in the eyes and ears, but the sharp pain of it is present.
An activated virus doesn't always cause a rash, but because it replicates on the nerve fibres near the skin, pain is very pronounced. Some people experiencing shingles will have a "prickly" pain of the skin, with no rash.
Leukopenia leaves a person susceptible to illnesses such as strep throat, pneumonia and other, more serious infections. If the white blood cells are completely obliterated, infections not normally seen---known as "opportunistic infections"---may develop, including thrush (a fungal infection of the mouth and throat) and mycobacterial infections, which can cause tuberculosis.