Steroids are usually employed to inhibit inflammation. However, allergic contact dermatitis has been reported with topical steroids. We have experienced contact dermatitis due to active ingredients of topical steroids in 11 patients. Therefore, we make it a rule to carry out the patch test with as many topical steroids as possible. Five patients were confirmed to be positive to several corticosteroids in the patch test. Papers on patients allergic to steroids indicate that some patients react to several. It is difficult to evaluate whether the reaction is caused by multisensitivity or by cross reaction. However, even if steroids differ in type, they may often cause cross reactions when they have a common chemical structure. Considering this chemical structure, we tried to classify steroids reported to cause allergy in patients into the following four types: 1) The type recognizing betamethasone and/or dexamethasone. Regardless of whether the methyl group at the C-16 position of the D ring is on the alpha or beta side, the size of the blocking group of the hydroxy residue seems to be associated with the reaction. 2) The type in which a chlormethylketone group at the C-17 position of the D ring seems to be associated with the reaction. 3) The type in which a cis-diaxial-diol side chain in the alpha side of C-16 and C-17 positions of the ring D or its ketal blocking group seems to be associated with the reaction. 4) The type in which the size of the ester protecting the hydroxy group at the C-17 alpha position seems to be associated with the reaction. In patients showing a reaction, there may be receptors recognizing each steroid. If the steroid administered is changed, the receptor appears to recognize the changed steroid in a relatively short period. Thus the receptor may not be constant.
