Causes of post-herpetic neuralgia
The varicella zoster virus causes both chickenpox and shingles.
In post-herpetic neuralgia, the virus causes inflammation of the nerves under the skin of the affected area. Neuralgia is a medical term for pain resulting from nerve inflammation or damage.
It's not clear why some people with shingles develop post-herpetic neuralgia, but increasing age, pain during the early stage of shingles and severe pain throughout an episode of shingles are all associated with an increased risk of the condition.