First Human Pheromone Spotted

Women of reproductive age secrete substances from their armpits that appear to delay or accelerate the menstrual periods of other women. The finding, reported in tomorrow's issue of Nature, is the strongest evidence yet that people, like many other animals, release and respond to volatile chemicals called pheromones.
      In 1971, researchers discovered that the menstrual cycles of women living together tended to become synchronized over time, but no one had been able to pin down how this synchrony came about. To collect possible pheromones, the researchers--University of Chicago psychologists Martha McClintock and Kathleen Stern--had nine women wear pads under their armpits for 8-hour stints during different phases of their menstrual cycles. The researchers then disinfected the pads with alcohol and froze them, taking a gamble that the pheromones, if present, would remain intact.
      Each day, the researchers rubbed the odorless pads above the upper lip of 20 women with regular menstrual periods. For 2 months, 10 women sniffed residue from pads collected early in a cycle, before ovulation, while the other 10 women were exposed to secretions collected after ovulation. The protocol was then reversed, with subjects exposed for 2 months to pads from the half of the menstrual cycle opposite to that of which they first sniffed. During the experiment, neither the subjects nor the researchers knew the origin of the pads.
      Fourteen of the women had shorter menstrual cycles when exposed to secretions collected before ovulation, and they experienced a delayed menstruation when exposed to pads from women who had already ovulated. Hormone measurements indicated that the shift was due to a change in when the women ovulated. The change averaged 2 days shorter or longer, but the range was up to 2 weeks. The menstrual cycles of six women did not change at all in response to the pads. The researchers have not yet isolated the putative pheromones.
      The work "shows for the first time that people can communicate with pheromones," says Aron Weller, a psychobiologist at Bar-Ilan University in Ramat Gan, Israel. McClintock suggests that if these pheromones, once isolated, work in women with irregular periods, they may improve their fertility by regulating ovulation.

Definitions from the AP Dictionary of Science and Technology