The underlying cause of any type of neuralgia is damage to a nerve. Each nerve in your body is protected by a coating called the myelin sheath. When the myelin is damaged or wears away from the nerve, the stabbing, severe, shock-like pain of neuralgia results. There are many different factors, including old age, which can cause damage to the myelin. Unfortunately, in many cases of neuralgia, a cause can never be found.

Infection
The cause of postherpetic neuralgia is shingles, an infection caused by the chickenpox virus. The likelihood of having this infection increases with age. Lyme disease, HIV, and syphilis can also cause neuralgia.

Multiple Sclerosis
Multiple sclerosis (MS) is a disease that is caused by the degradation of myelin. Among the many symptoms that result from MS is neuralgia, often in the face.

Pressure on Nerves
The myelin on nerves can be worn away by pressure. The pressure may come from a bone, ligament, blood vessel, or a tumor that is pressing on the nerve. The pressure of a swollen blood vessel is a common cause in trigeminal neuralgia.

Diabetes
Many people with diabetes will suffer from some type of neuralgia because excess glucose in the bloodstream can lead to myelin damage.