Skin Disorders Guide

Categories of Pruritus

Patients with pruritus can be divided into avo major groups, those with and those without associated, readily visible skin disease. In either case, episodes of pruritus may occur spontaneously or may be precipitated by excessive skin dryness (xerosis), retained sweat, or psychologic factors such as anxiety or depression. Again, in either case, the severity of the pruritus waxes or wanes depending on the degree to which the mind is occupied with other matters. Thus, patients with pruritus of all types generally indicate that the itching is most severe in the evening and at night.

Therapy For Pruritus

The treatment of itching is difficult. Topically applied steroids are of help only in those cases where there is accompanying inflammation. Cool soaks (bathtub immersion) provide quick but short-lived relief. Commercial lotions provide a cooling effect, and if agents such as camphor and menthol are added, there may also be an acupuncture-like effect wherein a new sensation blocks the sense of itching. Topical anesthetics are sometimes used, but the effect is not marked, and there is some risk of inducing allergic contact dermatitis with some of the agents. Pramoxine (Prax) is widely used, but I have not found it to be very helpful.

Ultraviolet light of either UVB or UVA wavelengths was originally used for the treatment of pruritus associated with liver disease. Subsequently, it has successfully been used for many forms of itching.

Orally administered antihistamines represent the pro typical approach to the treatment of pruritus. The newer nonsedating antihistamines have relatively little effect (except in urticarial itching), however, suggesting that antihistamines work through a central nervous system mechanism. Various psychopharma­cologic medications (both anxiolytic and antidepressant agents) are also very helpful in controlling itching.

The most exciting approach to the treatment of pruritus relates to the development of agents that have an effect on the specific chemical transmitters of the itch impulse. Perhaps this is the method of action for the sedating-type antihistamines and psychotropic agents, but if so, these seem to be fairly nonspecific. Capsaicin, a topically applied agent that depletes the neuropeptide substance seems to have some beneficial effect on pain and itch, this would appear to offer a somewhat more specific approach to the problem.