Tachyphylaxis to topically applied steroids.

Acute tolerance to the vasoconstrictive effect of topically applied glucocorticoids in humans has recently been described. Similar acute tolerance to the antiproliferative properties of topically applied steroids in proliferating and normal hairless mouse epidermis is now shown to occur. Thus, at first, topically applied steroids cause profound inhibition of DNA synthesis and mitosis in the epidermis, but with continued treatment, DNA synthesis and mitosis recover and the tissue becomes insensitive to further stimulation. This suggests that there is an optimum approach to therapy with topically applied steroids that might reduce the incidence of side effects and improve therapeutic efficacy.