Chronic pruritus in the absence of specific skin disease: an update on pathophysiology, diagnosis, and therapy.

Chronic pruritus is a major and distressing symptom of many cutaneous and systemic diseases and can significantly impair the patient's quality of life. Pruritus perception is the final result of a complex network involving dedicated nerve pathways and brain areas, and an increasing number of peripheral and central mediators are thought to be involved. Itch is associated with most cutaneous disorders and, in these circumstances, its management overlaps with that of the skin disease. Itch can also occur without associated skin diseases or primary skin lesions, but only with nonspecific lesions secondary to rubbing or scratching. Chronic itch with no or minimal skin changes can be secondary to important diseases, such as neurologic disorders, chronic renal failure, cholestasis, systemic infections, malignancies, and endocrine disorders, and may also result from exposure to some drugs. The search for the cause of pruritus usually requires a meticulous step-by-step assessment involving careful history taking as well as clinical examination and laboratory investigations. Few evidence-based treatments for pruritus are available. Topical therapy, oral histamine H(1) receptor antagonists, and phototherapy with UV radiation can target pruritus elicitation in the skin, whereas antiepileptic drugs, opioid receptor antagonists, and antidepressants can block signal processing in the CNS.