Pruritus (itching) is an unpleasant sensation that elicits the desire to scratch. It is a distressing symptom that can cause discomfort and threaten the effectiveness of the skin as a major protective barrier. Because of the subjective nature of pruritus, the lack of a precise definition, and the lack of suitable animal models, pruritus is a disorder that has not been researched adequately.

The skin accounts for 15% of the body's total weight and is the largest organ of the body. The skin has significant psychosocial and physical functions. Its function as a protective mechanism is the skin's most important role. But skin is also essential to self image and one's ability to touch and be touched, thereby providing an important component of communication.

Symptoms of generalized itching, without rash or skin lesions, may be related to anything from dry skin to an occult carcinoma, and the etiology of the symptoms should be explored. Common nonmalignant etiologic factors include drug reactions, xerosis, scabies, and primary skin diseases. Pruritus is one of the most common complaints of the elderly patient, but estimates of the significance of pruritic symptoms in the elderly population vary from 10% to 50%. The most common diagnosis related to pruritus in this population is simply dry skin.[1]

Generalized pruritus is found in about 13% of all individuals with chronic renal disease and about 70% to 90% of those undergoing hemodialysis for its treatment.[2] Cholestatic liver disease with intrahepatic or posthepatic obstruction, with or without increased serum levels of bile acids, is often associated with pruritus.[3] Other etiologic factors include (but are not limited to) primary biliary cirrhosis, cholestasis related to phenothiazines or oral contraceptives, intrahepatic cholestasis in pregnancy, and posthepatic obstruction.[3]

References:

1. Duncan WC, Fenske NA: Cutaneous signs of internal disease in the elderly. Geriatrics 45 (8): 24-30, 1990.
2. Blachley JD, Blankenship DM, Menter A, et al.: Uremic pruritus: skin divalent ion content and response to ultraviolet phototherapy. Am J Kidney Dis 5 (5): 237-41, 1985.
3. Abel EA, Farber EM: Malignant cutaneous tumors. In: Rubenstein E, Federman DD, eds.: Scientific American Medicine. New York: Scientific American, Inc, Chapter 2: Dermatology, Section XII, 1-20, 1992.