Topically applied glucocorticoids (corticosteroids) elicit a pharmacologic activity (blanching) viewed by many as being "vasoconstrictive" in nature. This pharmacodynamic response has been correlated with the clinical efficacy of the product1-3 and has been used to determine the bioavailability of topical glucocorticoid preparations.4 Glucocorticoids, when applied topically on human skin, undergo percutaneous absorption resulting in apparent vasoconstriction of superficial vasculature and skin blanching. While the precise mechanism of action is unknown, the observed pharmacodynamic response is the blanching effect. It might, therefore, be more accurate to refer to this assay as the skin-blanching assay rather than the vasoconstriction test.
The blanching effect has been used as a measure of the percutaneous "absorption" or "potency" of glucocorticoids from topical formulations and has been used in evaluating and selecting optimum formulations.5-7 On the basis of intensity of blanching, an arbitrary score of 0,1, 2, or 3 is assigned, 0 indicating
Shah VP, Peck CC, Skelly JP. `Vasoconstriction'—Skin Blanching—Assay for Glucocorticoids—a Critique. Arch Dermatol. 1989;125(11):1558-1561. doi:10.1001/archderm.1989.01670230100019