ABSTRACT
Post-herpetic neuralgia (PHN) is a chronic pain which can occur following acute herpes zoster infection (shingles). Herpes zoster infection results from reactivation of the varicella zoster virus, dormant in perineural tissues following a primary chickenpox infection. Acute herpes zoster infection may be painful, although 40% of patients do not report pain. PHN is pain persisting after the pain of the acute infection. The demarcation between pain due to acute infection and the pain of PHN is not defined. Some define pain persisting beyond the crusting of acute infective lesions as PHN; others, pain after specified periods from 4 weeks to 6 months since the eruption of acute infective skin lesions. There is therefore no clear definition of PHN.
