I see a new male deodorant coming to market.
Rice University researchers Wen Zhou and Denise Chen had 20 heterosexual men place small absorbent pads in their armpits while watching pornographic videos (Sexual arousal was confirmed using electrodes.) Next, the men swapped out the pads for fresh ones to absorb sweat while they weren't aroused.
Later, the researchers had 19 women sniff the pads while being monitored by fMRI. The result? The women's brains appeared to distinguish between the sweat of aroused men and unaroused men.
The finding doesn't mean that women can consciously perceive this difference, but it does indicate that the difference does, at least, register subconsciously.
The study was published in the December 31 issue of the J of Neuroscience. Abstract