Since the discovery that women's menstrual cycles could be synchronized and the cause of the synchrony was thought to be some type of pheromone, the debate over the existence and the effect of pheromones in humans has raged on. Especially, how pheromones may affect human sexual behavior.

Although conclusions of the various studies remain controversial they do seem to confirm that at least two chemicals found in human sweat have an affect on the brain and possibly a third.

Androstadienone a testosterone like substance found in men's sweat boosts hypothalamic activity only in women. While estratetraenol an estrogen like substance found in women's sweat boosted hypothalamic activity only in men, according to a study from the Karolinska Institute in Sweden. The hypothalamus influences the pituitary gland's release of hormones. And as you are well aware, hormone levels play a key role in sexual behavior.

In another study at UC Berkeley, women who sniffed androstadienone reported an improved mood and significantly higher sexual arousal. The women also experienced increases in blood pressure, heart rate and breathing.

Elevated levels of cortisol were also noted in the women. The cortisol levels rose within 15 minutes of sniffing the androstadienone and remained elevated for over an hour afterwards. Researchers don't know which came first-the change in cortisol levels which then induced the improved mood and significant increase in sexual arousal; or was it the improved mood and significant increase in sexual arousal that caused the rise in cortisol levels?

Unlike animals, humans don't reflexively act upon sexual urges triggered by pheromones. More research out of Switzerland shows the human sexual arousal response has a governing component-like the accelerator and brake on a vehicle. We consciously and subconsciously, depending on our experiences and choices, allow our sexual desire to rise in response to our physical and mental sexual arousal or put on the brakes.

Other recent discoveries show how a pheromone in sweat that may affect your sex life is testosterone. Research out of Brock University in Canada noted that when men sweat during vigorous exercise they excrete small amounts of testosterone. When the exercise is sex, the amount of testosterone excreted was ten times higher. In fact the levels of testosterone were almost as high as the amount in a testosterone cream a doctor would prescribe to enhance the libido of a woman who had had her ovaries removed.

Professor Muir theorizes testosterone may act as a pheromone in humans. He says "During sweaty sex, a man might transfer his testosterone to the female, turning her on even more."

This could also explain why women who engage in vigorous sweaty sex, may have more sex. Her sex life is acting as an aphrodisiac. She may be getting a boost in her testosterone levels and libido by absorbing the testosterone excreted by her male partner and absorbed through her skin. Muir's research indicates there are steroid receptors beneath the skin. "If you can drip sweat bursting with testosterone onto a female's belly during sex, this might explain what's going on," said Muir.