Definition: Tachyphylaxis is the tolerance the skin develops to the vasoconstrictive action of topical steroids. After repeated use of topical steroids, the capillaries in the skin do not constrict as well, requiring higher doses or more frequent application of the steroid. With high-potency steroids this effect has been documented after 4 days of applying a topical steroid three times a day. The ability of the blood vessels to constrict returns 4 days after stopping therapy.
Pronunciation: TACK-ee-fill-AX-sis - noun