Dorsal skin reactions of hairless dogs to topical treatment with corticosteroids

Dorsal skin reactions to continuous topical treatment with different types of corticosteroids were histologically investigated in hairless descendants of Mexican hairless dogs. The preparations tested were prednisolone (ST-1; weak). fluocinolone acetonide (ST-2; moderate), diflucortolone valrerate ( ST-3; strong), and mometasone furoate (ST-4; very strong). Grossly, the sit es treated with ST-3 and ST-4 showed moderate inflammatory reactions. After completion of the corticosteroid treatment, both sites were less pigmented and had a thin texture. The severity of histologic changes in the skin was dependent on the efficacy of the corticosteroids. The epidermis was promin ently thinned from 1 wk after treatment with the corticosteroids, resulting in a flat dermis-epidermis junction. By the end of the corticosteroid trea tment. these lesions became progressively more severe. At 2 wk after comple tion of topical treatment, the epidermal thickness in the sites treated wit h ST-1 and ST-2 began to return to normal values, whereas the epidermis of the skin treated with ST-3 and ST-4 became thinner. At 3-4 wk after topical treatment with ST-3 and ST-4, the dermis showed hyalinization of collagen bundles. These dermatologic findings in hairless dogs are in accordance wit h steroid-induced skin atrophy of human beings. These results suggest that the skin of hairless dogs responds sensitively to topical corticosteroids a nd that these animals are a useful model for investigating the efficacy and adverse effects of cutaneous topical corticosteroids.