The main components of human axillary odor are unsaturated or hydroxylated branched fatty acids with E-3M2H (E-3-methyl-2-hexenoic acid) and HMHA (3-hydroxy-3-methyl-hexanoic acid), sulfanylalkanols and particularly 3M3SH (3-methyl-3-sulfanylhexan-1-ol), and the odoriferous steroids androstenone (5α-androst-16-en-3-one) and androstenol (5α-androst-16-en-3α-ol) [REF].
Body odor is influenced by the actions of the skin flora, including members of Corynebacterium, which manufacture enzymes called lipases that break down the lipids in sweat to create smaller molecules like butyric acid.