Chronic pruritus: clinics and treatment.

Chronic pruritus, one of the main symptoms in dermatology, is often intractable and has a high impact on patient's quality of life. Beyond dermatologic disorders, chronic pruritus is associated with systemic, neurologic as well as psychologic diseases. The pathogenesis of acute and chronic (>6 weeks duration) pruritus is complex and involves in the skin a network of resident (e.g., sensory neurons) and transient inflammatory cells (e.g., lymphocytes). In the skin, several classes of histamine-sensitive or histamine-insensitve C-fibers are involved in itch transmission. Specific receptors have been discovered on cutaneous and spinal neurons to be exclusively involved in the processing of pruritic signals. Chronic pruritus is notoriously difficult to treat. Newer insights into the underlying pathogenesis of pruritus have enabled novel treatment approaches that target the pruritus-specific pathophysiological mechanism. For example, neurokinin-1 antagonists have been found to relieve chronic pruritus.