Gender-specific induction of enhanced sensitivity to odors.

Induction of olfactory sensitivity in humans was first illustrated when men and women who were initially unable to smell the volatile steroid androstenone (5alpha-androst-16-en-3-one) developed that ability after repeated, brief exposures. Because this finding has not been replicated with other compounds in humans, it has been assumed that olfactory induction is a narrowly constrained phenomenon, occurring only in individuals with specific anosmias, perhaps only to androstenone (compare ref. 2). Here we show that induction of enhanced olfactory sensitivity seems to be a more general phenomenon, with marked changes in olfactory acuity occurring during repeated test exposures to several odorants among people with average baseline sensitivity to these compounds. This increased sensitivity (averaging five orders of magnitude) was observed only among females of reproductive age. These observations provide convincing evidence that female olfactory acuity to a variety of odorants can vastly improve with repeated test exposures. They also suggest a sensory basis for the anecdotal observation of greater olfactory sensitivities among females and raise the possibility that the olfactory-induction process may be associated with female reproductive behaviors such as pair bonding and kin recognition.