The present invention provides a substance which promotes the transdermal absorption of a pharmacologically active component while little irritating the skin. The present invention relates to a transdermal absorption promoter which comprises as the active component at least one member selected from among isopulegol 2-(menthoxy)ethanol and 2-methyl-3-(menthoxy)propane-1 2-diol and an external skin formulation which comprises a pharmacologically active component such as a psychotropic component an anti-inflammatory component an analgesic component an antipyretic component a whitening component or a hair growth-promoting component together with the aforesaid transdermal absorption promoter.
