CATANIA, Italy, Oct. 25 (UPI) -- A new study suggests some women may not be in the mood for sex because the oral contraceptives they take could be blocking their sense of smell.
A team of Italian researchers at the University of Catania said oral contraceptive use can blunt a woman's sense of smell, particularly during ovulation when sense of smell is highest.
Scientists came to this conclusion by studying 60 women, ages 18 to 40, who did not take birth control pills. Their ability to detect six distinct substances -- anise, musk, clove, ammonia, pyridine, which is a chemical used in many household products, and citral -- were measured three times during their menstrual cycles. Sense of smell heightened during ovulation, researchers found.
The women were then placed on oral contraceptives for three months. Their sense of smell was measured again on days seven, 14, 21 and 28 of their 28-day cycles.
While on birth control pills, the women showed no difference in smell sensitivity throughout the study period. It did not increase during ovulation as it had prior to oral contraceptive use, researchers report in the Oct. 26 issue of Human Reproduction, a journal of the European Society for Human Reproduction and Embryology.
Speaking through an interpreter, researchers Luigi Maiolino and Giorgia Intelisano told United Press International smell is key for sexual arousal in most species, including humans.
"People who take the pill, this increased sense of smell that jumps prior to ovulation was never there," Maiolino said. "It was reduced."
It is possible, the researchers added, that smell sensitivity might be blunted because progesterone, a hormone used in oral contraceptives and found naturally in the body, could be interfering with the ability to smell.
But researchers cautioned more study is needed and smell is not all that drives libido. "It's not easy to establish all the component parts of libido," Maiolino explained.
If and how oral contraceptive use might impact libido has long been debated in this country. Dr. Yvonne S. Thornton, senior perinatologist and a board-certified obstetrician-gynecologist at St. Luke's-Roosevelt Hospital in New York, said human sexuality is far more complicated than one's ability to smell an attractive mate.
"That's not to say it's free of any culpability of smell, of libido," Thornton told UPI. "We all know it's more complicated than that."
Hormone dosages in oral contraceptives, she added, are so low it is unlikely they are the direct cause of reduced sex drive. The pill, Thornton said, is "always being blamed."
The Italian team pointed out smell has played a decreased role in sexuality over the centuries as men and women bathe more frequently and cover their natural scents with manufactured products. Humans today, Maniolino said, "are camouflaged by perfumes, deodorants."
The most important body part in sex, Thornton said, is not the nose, but the brain. A woman's sex drive is "not just smell. It's the environment. It's the partner. It's foreplay," she said. "Sex is psychological."
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(Reported by Katrina Woznicki in Washington.)
