“…When investigating the allergens characteristic of the domestic environment, McEwen (1968) showed they were contained in old keratin material, though when the work was done it was 327 not realized that the keratin, whether from feathers, hair, or human skin scales, served only as a source of food for mites. Soon after, it was shown (Frankland, McEwen, and Feinberg, 1970) that a mite extract of D. farinae could be used as a diagnostic skin test agent in house dust sensitivity.…”