Pheromones are naturally occurring substances the fertile body excretes externally, conveying an airborne message to trigger a sexual response from a member of the same species.

A mystery chemical isolated from the sweat of young women seems to act as a romance booster for their older counterparts. When the researchers added the compound, Pheromone 10:13, to a perfume and gave it to older women, it made their partners more affectionate. In diaries kept by the women for 6 weeks, 41 percent of pheromone users reported more petting, kissing and affection with partners. Pheromones are airborne chemicals secreted from the body and recognized by their smell. Humans and animals emit pheromones. Joan Friebely of Harvard University and Susan Rako, a doctor from Newton, Massachusetts, studied the behavior of 44 post-menopausal women. Half were given a perfume with the compound while the remainder used a fragrance with a placebo or dummy chemical. Only 14 percent of women using the perfume with the placebo reported an increase in affection from their partners. Biologist Winnifred Cutler, the discoverer of the mystery pheromone, is keeping the identify of the compound a secret until patents have been granted to her organization, the Athena Institute for Women's Wellness Research in Chester Springs, Pennsylvania, according to the magazine.

Androstenone as a pheromone
Androstenone is made when the body breaks down the male sex hormone testosterone. Androstenone is in the sweat of men and women, but it is more highly concentrated in men. Androstenone facilitates the courtship behavior in females. Hiroaki Matsunami of Duke University in North Carolina and his colleague tested sweat chemicals on most of the 400 known odor receptors used by the nose to sniff out smells and chemicals. They found the odor receptor gene called OR7D4 reacted strongly with the sex steroid androstenone. Next, they tested whether variations in this gene had an impact on how people perceived the smell of androstenone in male sweat. They took blood samples and sequenced the DNA of 400 people who participated in a smell perception test. What they found is slight genetic variations determine whether androstenone has a pungent smell, a sweet, vanilla-like smell or no smell at all. The same sweat in a man can be neutral, attractive, or unpleasant to different women.

Pheromones tested in Lesbians and Gay Men
Lesbians’ brains react differently to hormones than those of heterosexual women, perhaps similar to heterosexual men. Research appears to confirm homosexuality has a physical basis and is not learned behavior.
     The research team led by Ivanka Savic at the Stockholm Brain Institute had volunteers sniff chemicals derived from male and female sex hormones. These chemicals are thought to be pheromones — molecules known to trigger responses such as defense and sex in many animals. The same team reported last year on a comparison of the response of male homosexuals to heterosexual men and women. They found that the brains of gay men reacted more like those of women than of straight men. The new study shows a similar, but weaker, relationship between the response of lesbians and straight men. Heterosexual women found the male and female pheromones about equally pleasant, while straight men and lesbians liked the female pheromone more than the male one. Men and lesbians also found the male hormone more irritating than the female one, while straight women were more likely to be irritated by the female hormone than the male one. The research was funded by the Swedish Medical Research Council, Karolinska Institute and the Wallenberg Foundation.