Postherpetic neuralgia is a painful, often excruciating condition caused by the damage that the varicella zoster virus causes to the affected nerves during and after an attack of herpes zoster (shingles). It usually manifests itself after the pustules have started to die down. The pain is not controlled by traditional painkillers such as opiates and other analgesics as it is a fundamental (neuropathic) nerve pain.

There are few treatment options for PHN aside from gabapentin and other such anticonvulsants. There are some experimental treatments which are admittedly sporadic in success, such as rhizotomy (severing or damaging the affected nerve to relieve pain), TENS (a type of electrical pulse therapy), and other medication such as topical capsaicin lotion.

Anecdotal testimonies from patients have suggested that smoking marijuana relieves the pain in much the same way as it relieves the pain of multiple sclerosis.