The investigation and treatment of anogenital pruritus.

The patient with anogenital pruritus sets a difficult diagnostic problem for several reasons. This symptom may be due to one or more of a motley group of causes, ranging from outward irritation from parasites, fungous and coccal infections, chemicals and local skin diseases, through more general causes including toxic states, metabolic disorders, and nutritional deficiencies, to the other extreme of psychogenic irritation caused by an unresolved psychosexual conflict. Similar or even identical physical signs may result from many different causes and they indicate psychophysical type reactions of the patient rather than the nature of the cause. Thus, a follicular eruption may arise from nutritional deficiency, chemical insult, bacterial and fungous infection with or without obvious physical injury, or from an emotional upset. Often the action of two or more of these noxae coincides and the status seborrhoeicus represents the resultant lowered resistance of the follicles to infection with banal organisms. Vitamin B, iron and protein deficiencies account for a proportion of cases of this sort but the remainder are relatively or completely 'unresponsive to nutritional therapy. Pruritus usually, but not always, leads to scratching or rubbing, but the results of physical injury to the skin differ from one individual to another, so that eczema may result in one, lichenification in another, a seborrhoeic eruption in a third, and psoriasis in yet another if the sufferer happens to be a latent or overt psoriatic. The physical signs may be aggravated, altered or masked by secondary infection with bacteria and fungi or by injudicious treatment, especially with benzocaine surface anaesthetics, sulphonamides, mercurial antiseptics and fungicides, penicillin, phenol and other bactericidal and fungicidal agents. The condition found on examination may be the cause of the pruritus, or the result of subsequent physical or chemical damage, or infection, and the primary condition can then only be diagnosed after the clearance of the secondary dermatosis. Mildly infected eruptions demonstrate this difficulty very well. They may arise from the primary cause, such as malnutrition or chemical irritation from vaginal douche or contraceptive. They may also be due to secondary infection from scratching and rubbing or from the application of therapeutic irritants which set up a chemical dermatitis which soon becomes infected. The paradox of infected chemical dermatitis from antiseptic topical agents is explained by the harmful effect of many of these substances on epidermal cells, leading to a reduction of the self-disinfecting properties of the skin. Physical examination may reveal a specific skin disease, or a skin reaction which gives a hint of the cause of the pruritus and suggests further lines of investigation. But 'Qui bene interrogat, bene diagnoscit' remains the guiding principle because only a comprehensive history can give the necessary positive information upon which an accurate diagnosis is based. This applies to all types but especially to the psychogenic cases, the diagnosis of which is only made on positive evidence. Leading questions have to be put, to exclude nutritional, contact irritant and psychogenic causes. Anogenital pruritis may be discussed under the following headings:--pruritus vulvae, pruritus vulvae et ani, pruritus scroti et perinei, pruritus ani.