Corticosteroids are among the most commonly used drugs, both topically and systemically. Although unexpected and paradoxical, allergic hypersensitivity to corticosteroids is a common finding, delayed-type reactions being much more frequently encountered than the immediate-type ones. With regard to cross-reactions between corticosteroids, based on patch-test results and molecular modelling, we were recently able to simplify the previous classification into 3 different groups, i.e., Group 1: the non-methylated, most often nonhalogenated molecules (Group A, D2 and budesonide), which produce most of the allergic reactions; Group 2: the halogenated molecules with a C 16/C 17 cis ketal/diol structure (acetonide Group B); and Group 3: the halogenated and C 16-methylated molecules (Group C and D1) that only rarely produce allergy.
Baeck, M., & Goossens, A. (2012). New insights about delayed allergic hypersensitivity to corticosteroids. Giornale Italiano di Dermatologia e Venereologia : a journal on dermatology and sexually transmitted diseases, 147(1), 65-69. https://hdl.handle.net/2078.5/205313 (Original work published 2012)