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Summary.— Using an instrument designed to exert known pressures on the skin, an incidence survey of factitious wealing in the general population has been carried out; 2813 subjects have been tested with a pressure of 4900 g/cm2, and the overall incidence was 4·24% (females, 5·2%; males, 4·34%). The incidence did not vary significantly in the different age groups. A series of patients with symptomatic dermographism has been followed up in the outpatient Department and serial measurements of the weal size have been made. In 20 of these comparable measurements are available over prolonged periods. The total number of patients showing at least 50% reduction in weal size was: at 2 months, 1; at 4–6 months, 7; at 6–9 months, 10; at 9–12 months, 12. The incidence of factitious wealing in various patterns of urticaria is mentioned and the results of the incidence survey are discussed in relation to patients presenting with symptomatic dermographism.

Regular measurements of the weal size produced by known trauma have been carried out in a series of patients with symptomatic dermographism. The degree of reduction of the weal has been compared after 2 weeks’treatment with chlorpheniramine and hydroxyzine pamoate administered in a double blind manner to thirty‐three patients. The doses given were those in common usage and usually well tolerated by patients, namely chlorpheniramine 4 mg three times daily and hydroxyzine pamoate 25 mg three times daily. Hydroxyzine gave a statistically greater reduction of weal size and was also clinically preferred. Hydroxyzine is a weak antihistamine and its mode of action on weal production is unknown, but its clinical efficacy is not likely to be due to its sedative effects. Statistical proof is given to the observation that weals on exposed sites are smaller than those provoked in areas of skin normally covered.

SUMMARY.— When a weal evoked as a cutaneous allergic response has disappeared, that area of skin, although appearing normal, shows factitious wealing: this tendency persists for 72–96 hr. The phenomenon is present after weals caused by positive intradermal prick tests from various substances, after weals from certain insect bites, and on the site of fading lesions of acute urticaria. Weals caused by intradermal histamine are not followed by this factitious wealing, nor is it present on skin which has been the site of a weal in chronic urticaria.

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