Axillary odour, also known as fox odour, is mainly due to the production of unsaturated fatty acids from the secretions of the sweat glands in the axillae by the action of dermal epithelial bacteria, resulting in an abnormal odour. It is not always the sweaty armpits that cause fox odour, but the main differentiator is whether the sweating produces unsaturated fatty acids through bacteria and gives off an abnormal odour.