You can smell it
"The present studies suggest that men are sensitive to the olfactory signals of sexual arousal released by women. This research suggests that these signals released along with corresponding visual and auditory expressions of sexual interest can produce a stronger overall signal that increases sexual motivation," said Dr. Arnaud Wisman, a Psychologist at the University of Kent.
"Sexual interest may entail more than meets the eye and we hope that the current findings encourage further research to examine the role of sexual olfactory signals in human communication."
The research saw three different experiments conducted where men were asked to evaluate the scents of axillary sweat samples from anonymous sexually aroused and non-aroused women. It turned out the men found the aroused samples more attractive.
"Experiment 1 revealed that men evaluate the axillary sweat of sexually aroused women as more attractive, compared to the scent of the same women when not sexually aroused," wrote the study.
Two further experiments then found that smelling a woman's sexual arousal increased both men's sexual arousal and sexual motivation. However, although men were more turned on by women who were aroused, this did not make them lose interest in those that were not.
"As predicted, men devoted greater attention to and showed greater interest in mating with women who displayed sexual cues (e.g., scantily dressed, in seductive poses). By contrast, exposure to the sexual chemosignals did not alter males’ attention and mating interest toward women who displayed no sexual cues," wrote the study.