Characterization and analysis of skin wealing by computerized non-linear regression.

Weal formation in human skin may be induced by histamine, histamine releasers and other inflammatory mediators. Weals occur spontaneously in chronic urticaria, and in response to frictional pressure in dermographic urticaria. We present an improved method for the analysis of wealing in human skin by the use of non-linear regression. The method has the advantage of speed, and by the use of non-linear regression permits the full characterization of the response curves. The time course of histamine-induced wealing is a double exponential function corresponding to the separate components of weal appearance and disappearance. Dermographic wealing corresponds to an increasing exponential function with increasing pressure. The method of computerized non-linear regression is a considerable advance on previous methods for the analysis of urticarial wealing, the effect of vasoactive agents, and their therapeutic action.