Pruritic Dermatoses: Overview of Etiology and Therapy

This review begins with a brief survey of the neuro-physiology and neuroanatomy of pruritus, and goes on to describe the etiology of the major allergic and nonallergic pruritic disorders. The etiology of pruri-tus often suggests the appropriate treatment. For example, urticaria, which is primarily mediated by histamine, is amenable to treatment with H1 antihis-tamines. Second-generation, nonsedating antihista-mines appear to be more effective than sedating antihistamines, perhaps because of better compli-ance. Other systemic pharmacologic options may be useful in nonhistamine-mediated disorders, for ex-ample, immunomodulators for inflammation-induced pruritus or opiate antagonists for atopic dermatitis. Nonpharmacologic measures, such as proper skin care, and physical modalities, such as phototherapy or acupuncture, may also be helpful. Am J Med. 2002;113(9A):25S–33S. © 2002 by Excerpta Medica, Inc. The skin reacts to physical and inflammatory stim-uli in only a limited number of ways. The sensa-tion of itching, or pruritus, is the most common symptom of dermatologic conditions. In 1660, the Ger-man physician Samuel Hafenreffer defined itching as an “unpleasant sensation that provokes the desire to scratch, ” and although this definition has been modified to correlate with current knowledge, it remains a reason-able one.1 Pruritus is the subjective sensation of itching. The types and causes are complex and not yet completely understood. Perhaps the unfortunate plight of the itching patient is best described in this brief poem by Julian Ver-bov2: I itch, I itch, the whole day through I also itch at night. I try so hard to stop myself I’m looking such a sight. To itch is not so nice you know, It really is deplorable But to scratch is really something That is often quite enjoyable. The sensation of itch is the common factor in a multi-tude of diverse cutaneous disorders. Histamine is the pri-mary mediator of itching in some types of allergic disease, but multiple agents or mediators can provoke itching in both allergic and nonallergic diseases. This review provides a brief overview of the pathogen-esis of itching, describes the major itching skin disorders related to allergic and nonallergic disease, and includes a discussion of nonpharmacologic and pharmacologic therapies