The compound believed to be principally responsible for the unpleasant odor sometimes produced during cooking of pork or bacon from boars has been isolated and identified as 5a-androst-16-en-3-one. It is the first mammalian pheromone to be identified. Androstenone is the active ingredient in a commercial products which were developed for farmers and breeders who need help determining the best fertilization time for sows and gilts. In humans, androstenone also has been suggested to be a pheromone. Excessive exposures may affect human health, as follows: Upper respiratory tract: Irritation, Dizziness, Drowsiness, Headache, Nausea; Skin: Redness.