Human pheromones: have they been demonstrated?

Efforts to collect evidence of human pheromones have focused on three partly overlapping classes of possible human pheromones: (1) axillary steroids, (2) vaginal aliphatic acids, and (3) stimulators of the vomeronasal organ. Examples of each of these classes have been patented for commercial use, and in some cases aggressively marketed, but there is only incomplete evidence supporting any particular claim that a substance acts as a human pheromone. The large axillary scent Glands found in humans appear to be well adapted for the production of pheromones, but may actually be used for non-pheromonal odor communication, such as the sharing of information about the immune system. Putative menstrual synchronization within social groups of women and putative acceleration of the menstrual cycle caused by men's odors may suggest the existence of human pheromone systems, but evidence in both cases is still inconclusive.