C(16)-methyl substitution, interfering with protein binding, and halogenation, seem to reduce the allergenicity of corticosteroid molecules. Hence, when indicated, C(16)-methylated corticosteroids should be preferentially prescribed.
Baeck, M., Chemelle, J.-A., Rasse, C., Terreux, R., & Goossens, A. (2011). C(16)-methyl corticosteroids are far less allergenic than the non-methylated molecules. Contact dermatitis, 64(6), 305-312. https://doi.org/10.1111/j.1600-0536.2011.01874.x (Original work published 2011)