Prurigo: diagnosis and management.

Prurigo is a condition of nodular cutaneous lesions that itch (pruire) intensely. Although the acute form can be caused by insect stings, most of the subacute and chronic forms appear to be idiopathic. Toxic agents deposited in the skin by exogenous factors such as parasites, bacteria, or topically or orally administered drugs can induce itch. In susceptible individuals, physical mechanisms such as UV light can induce changes in epidermal innervation that result both in itch generally and in prurigo lesions. Prurigo is sometimes associated with atopy, pregnancy, internal diseases, malabsorption, or malignancy. Some forms of prurigo may be secondary to scratching. Emotional factors can also influence the perception of itch and induce prurigo by provoking scratching. These are the various specialized forms of prurigo, and there are certain others, such as prurigo pigmentosa, that have some ethnic preference. Topical treatments by corticosteroids, coal tar, bath photochemotherapy, UVB, cryotherapy, or capsaicin, as well as systemic regimens involving use of psoralen + UVA (PUVA), erythromycin, arotinoid acid, cyclosporine, chloroquine, dapsone, minocycline, naltrexone, azathioprine or thalidomide are used for the treatment of this condition. Psychotherapeutic agents to treat problems of mood that deteriorate prurigo are also prescribed. Combined sequential treatments for generalized, therapy-resistant cases need to be tailored to the exacerbations that occur and to provide maintenance treatment in order to enable the patient to withstand the intolerable itch.