Topical Corticosteroid-Induced Skin Blanching Measurement: Eye or Instrument?

To the Editor.—  We have read with interest a recent critique¹ of the human skin blanching assay. We are concerned about the accuracy of statements and the interpretation of results presented in this publication. Having successfully employed this bioassay for over 15 years, and having noted similar, productive usage of this optimized technique reported^2,3 from laboratories worldwide, the negativism expressed in the critique could dissuade potential researchers from employing this extremely useful assay procedure.A major objection to our published methodology is that the intensity of blanching is estimated by the human eye. We agree that this is a highly subjective method, but we feel that if the optimized, double-blind methodology is rigidly applied, this problem is easily overcome. Emphasis has recently been made¹ of the alternative methods of reflectance spectrophotometry, laser Doppler velocimetry, and surface thermography as more accurate, objective techniques for the assessment of skin blanching. A