Post-herpetic neuralgia (PHN) is a condition characterized by persistent nerve pain that occurs after a person has experienced an episode of shingles (herpes zoster). Shingles is caused by the reactivation of the varicella-zoster virus, the same virus that causes chickenpox. After a person recovers from chickenpox, the virus can remain dormant in the body and later reactivate, causing shingles. During a shingles outbreak, a painful rash typically develops along a specific a