Hydrocortisone sensitivity. An investigation into the nature of the allergen

11 patients, positive to tixocortol pivalate on patch testing, were tested intradermally with a variety of hydrocortisone analogues. Substitution at the C21 position had no effect on the occurrence of positive reactions to hydrocortisone, whereas alteration of any of the carbon rings significantly reduced the number of positive reactions. We suggest that the C17 side chain is involved in protein binding and subsequent presentation of antigenic sites on the carbon rings.