Do human menstrual-cycle pheromones exist?

Research over the past 15 years indicates, contrary to earlier results, that women do not synchronize their menstrual cycles. If women do not synchronize their cycles, this implies there is no mechanism for synchronizing cycles. Since a pheromone mechanism of synchronization is the only plausible mechanism that has been proposed, it follows that that there are no pheromones that modulate the length of menstrual cycles. To test this hypothesis, eight studies were reviewed that reported pheromone effects on menstrual cycles, other behavior, or physiological correlates in women. The prediction was that serious problems would be found in each of these studies. As predicted, serious problems were found in all eight studies. Taken together, these results cast doubt on the existence of pheromones that modulate the length of menstrual cycles.