It has long been known that the use of hormones affects the sense of smell in humans, but this influence has been seen as general, that is, that the sensitivity to all smells is impacted to the same extent. The researchers study at the Department of Psychology, Uppsala university, metered the sensitivity of women to two odors, one that signals food (nourishment) and one considered to be a social smell, a pheromone that occurs naturally in male sweat. The results show that womens hormonal condition affects their sensitivity to different smells differently.

– Women on the pill were more sensitive to the smell signaling nourishment but less sensitive to the social smell, says Johan Lundström, one of the authors.

Moreover, this difference in sensitivity to smells seems to be linked to the degree of fertility. Women in the most fertile phase of their menstruation cycle were the most sensitive to the male sweat substance. The primary function of the sense of smell is considered to be that of a signal system that helps us, on the one hand, to choose what is edible and, on the other, to warn us about hazardous substances. This function has long been seen as the driving force behind the increased sensitivity of pregnant women to odors during the first few months of pregnancy. It is interesting that the hormone mix in contraceptive pills is largely identical to that in the body during the first months of pregnancy.

– This indicates that the enhanced sensitivity in women on the pill to the smell signaling nourishment is driven by the body´s desire to find nourishment for a fetus when the hormone balance signals pregnancy. The opposite may be true for women in the most fertile phase of their menstrual cycle, with greater sensitivity to the social smell. The driving mechanism there may be linked to a heightened interest in the opposite sex, says Johan Lundström.

More information: Johan Lundström, +46 (0)18-471 62 21, 070-580 65 71 or johan.lundstrom@psyk.uu.se