The invention provides a method of determining (or diagnosing) the presence or absence of a functional abnormality in the skin barrier, a kit therefor, a method of ameliorating a functional abnormality in the skin barrier based on the onset mechanism, and a drug therefor. The method of determining the presence or absence of a functional abnormality in the skin barrier comprises measuring the expression of a protease and/or an inhibitor thereof on the skin surface of a test object, and the like.
