Risk factors for postherpetic neuralgia (PHN) include: increasing age; a prodrome of pain before rash onset; the degree of spread of the rash, particularly if it extends beyond a single dermatome; and severity of pain during the acute attack. Forty per cent of patients over 50 and 75% of those over 75 develop PHN following resolution of the rash. Patients with severe pain or those whose condition is affecting their daily activities and function should be referred to a specialist in pain management.