Scientific research, writes Raj Kaushik, suggests that pheromones can inflict a romantic effect

SHILPA Shetty is turned off by it. Puja Batra hates it.

In fact, up to 90 per cent of the female respondents involved in sex surveys point out that male body odours are repulsive. But contrary to popular belief, recent scientific research suggests that body odours — pheromones, to give them their scientific term — can inflict a therapeutic, romantic, turn-on effect.

The word “pheromone” is derived from the Greek words pherein, meaning “to transfer”, and hormon, meaning “to excite”.

“Why do bulls and horses turn up their nostrils when excited by love?” Charles Darwin made this remarkable observation in his diary. In 1811, Ludwig Jacobson wrote about a tiny sensory organ located inside the nose near the nostrils in animals. This came to be called Jacobson’s Organ or the Vomeronasal Organ (VNO). Until recently, pheromones were best recognised in animals because of their ability to communicate with and attract members of the opposite sex. Female hamsters, for example, attract males by releasing pheromones in the greatest amounts just before they ovulate. The role of VNO in the case of humans has, however, remained ambiguous.

For example, Dr David Berliner, one of the founders of Pherin Pharmaceuticals, California, believes the VNO is an active organ in humans. On the other hand, Kunwar Bhatnagar, anatomical sciences and neurobiology professor at the University of Louisville, says human VNO cannot determine attraction to the opposite sex because it has no sensory cells.

Between these two extreme views lies a middle group of researchers who are unwilling to ignore the possibility that humans use chemicals to communicate with and attract their mates.

A 1998 study by the Athena Institute for Women’s Wellness Research in Chester Springs studied the sexual activity of 38 young to middle-aged heterosexual men while using pheromones. The users of pheromones, but not of an inactive control substance, reported that they had an increased frequency of informal dates, affectionate gestures such as sleeping next to a romantic partner, foreplay and sexual intercourse.

In 1971, Martha McClintock, a University of Chicago psychologist who was then an undergraduate at Wellesley College, published a study showing that the menstrual periods of women living together tended to adjust so that they fell on the same time every month. Now, more than 30 years later, McClintock and her colleagues are reasonably sure this convergence of menstrual periods is mediated by pheromones.

One of the most revealing studies in this context is Kathleen Stern and McClintock’s Regulation of Ovulation by Human Pheromones. In this study, underarm fluid samples of women were applied to the upper lips of other women in different phases of their menstrual cycles. The exposed women somehow adjusted their menstrual cycles to match. This phenomenon has also been documented in women’s prisons.

To determine the impact of steroid hormones on brain metabolism, McClintock and Suma Jacob conducted an interesting experiment. They recruited 10 women, aged 20 to 35, and tested each of them in separate two-day apart sessions. In the first session, the researchers applied a sample of a clove-propylene glycol solution mixed with the androstadienone under the women’s noses. Androstadienone is found in sweat, auxiliary hair, blood and semen. It is a common ingredient used in the manufacture of perfumes and colognes. The sample of the clove-propylene glycol solution without androstadienone was applied during the second session. The women were then put under a Positron Emission Tomography scanner. Those women who wore the androstadienone sample were seen to display an increased activity in regions associated with smell, vision, attention and emotion.

Scientist know that when female mice sniff around for a mate, they prefer males with immune system genes different from their own — which are called Major Histocompatibility Complex genes and produce antibodies. About five years ago, geneticist Carole Ober and colleagues examined the genetic make-up of 411 married American Hutterites couples. Descended from about 200 founders of an Anabaptist community in 1528, Hutterites have limited MHC gene variations. Surprisingly even in this narrow sample, Ober found fewer close MHC gene matches than would be expected by chance.

Because the Hutterites were apparently influenced by their partners’ genetic status in choosing spouses, Ober joined with McClintock to test if women could smell the difference in men’s MHC genes. They invited women to sniff T-shirts men had worn for two days. The used shirts were placed in boxes where they could be smelled but not seen. The women were asked which box they’d choose “if they had to smell it all the time”. They were not told they were going to smell a human odour. The outcome was outstanding. The women could actually smell differences in the men’s immune systems. They preferred the odour of men whose genetic make-up was close to their paternal genes, not to their maternal genes.

In a similar study, Swiss zoologist Claus Wedekind asked a group of female college students to smell T-shirts that had been worn by college males for two nights, without deodorant, cologne or scented soaps. In this study also, the women preferred the odours of men with dissimilar MHC, often commenting that it reminded them of an old boyfriend. They disliked the odour strongly when the man’s MHC was similar to their own, and often commented that it reminded them of a father or brother.

Julie Mennella of the Monell Chemical Senses Center in Philadelphia and her colleagues asked 45 women who never had given birth to sniff scented pads four times a day for a month. Then for the next two months, some women were randomly chosen to sniff breastfeeding pads. Twenty-six nursing mothers wore these pads in their bra and under their armpits. The women smelling the breastfeeding pads reported significantly heightened and more enduring sexual desires and fantasies. The study concluded that breastfeeding women and newborns gave off odours that aroused other women and encouraged them to reproduce.

Devendra Singh, a psychology professor at the University of Texas in Austin, gave a revere twist to the T-shirt study. He recruited female subjects and asked them not to wear perfume, avoid products and foods that would emit a strong odour, and refrain from sexual activity during the study. He asked them to wear one T-shirt at night during the most fertile phase of their menstrual cycle (13-15 days after their previous period), and then another T-shirt during the infertile phase of their cycle (days 21 to 22). After use, Singh presented the T-shirts to a group of men and asked them to rate the smell of the garments. They could detect a more “pleasant” or “sexy” smell in 15 of the 42 shirts. The smell of the other 27 T-shirts was considered unpleasant or not detectable.

This study seems to question advertisements that advocate the use of perfumes all over the body to attract males, and justify the power of natural pheromones, a favourite of Napoleon Bonaparte. Legend has it that when Napoleon wrote to Josephine to arrange a love tryst, he said, “I’m coming home — please don’t wash.”