1. What is postherpetic neuralgia (PHN)? Postherpetic neuralgia, also known as post-herpetic neuralgia, is a persistent neuralgia left after the healing of herpes zoster lesions, which can last for months, years, or even more than ten years, and is basically ineffective when treated with oral analgesics. It is called “malignant pain caused by benign disease”. 2. What is the mechanism of PHN? Herpes zoster is a respiratory virus infection, the virus is neurophilic varicella-herpes virus, infection into the blood latent in the sensory ganglion (brain ganglion or spinal nerve dorsal root ganglion), when the body resistance to decline, it will be in the sensory ganglion neurons and satellite cells in a large number of replication, and through the peripheral nerve spread to the skin, causing herpes zoster. In addition to the local skin, the sensory nerves are also damaged. The damaged nerves are prone to ectopic discharge, cross-myelination and central sensitization due to demyelination and scar formation, thus causing intractable neuralgia. 3. What are the clinical features of PHN? Herpes zoster is an infectious disease transmitted through the respiratory tract and can occur in all ages from children to the elderly, but only 9% to 13% of those left with sequelae PHN, and the incidence of PHN in patients with herpes zoster over 50 years of age can be more than 50%. PHN is typical of neurogenic pain and often manifests as spontaneous pain and abnormal sensory pain. The spontaneous pain is random and persistent pins and needles, knife-like, burning, electric shock-like pain or flashing pain, throbbing pain; abnormal sensory pain is manifested as nociceptive allergy or hypersensitivity: that is, the affected area of the skin by the slightest friction of clothing is painful. 4. Can PHN be cured? Herpes zoster is self-healing, the lesions (blisters) will heal on their own within 2-3 weeks without treatment, so the people are convinced that a “miracle doctor” can “cut the snake” by applying a circle of ink, drawing a charm, reciting a few incantations, and gesturing with a knife. In fact, it is because herpes heals naturally. Some people think that since it can heal itself, there is no need to treat it. In fact, it is the lesions that heal on their own, but the sequelae of PHN not only do not heal on their own, but are also very difficult to treat.