Body odor

Body odor or body odour (BO) is present in all animals and its intensity can be influenced by many factors (behavioral patterns, survival strategies). Body odor has a strong genetic basis, but can also be strongly influenced by various factors, such as gender, diet, health, and medication. The body odor of human males plays an important role in human sexual attraction, as a powerful indicator of MHC/HLA heterozygosity. Significant evidence suggests that women are attracted to men whose body odor is different from theirs, indicating that they have immune genes that are different from their own, which may produce healthier offspring. Biochemistry of body odor In humans, the formation of body odors is caused by factors such as diet, sex, health, and medication, but the major contribution comes from bacterial activity on skin gland secretions. Humans have three types of sweat glands: eccrine sweat glands, apocrine sweat glands and sebaceous glands. Eccrine sweat glands are present from birth, while the latter two become activated during puberty. Among the different types of human skin glands, body odor is primarily the result of the apocrine sweat glands, which secrete the majority of chemical compounds that the skin flora metabolize into odorant substances. This happens mostly in the axillary (armpit) region, although the gland can also be found in the areola, anogenital region, and around the navel. In humans, the armpit regions seem more important than the genital region for body odor, which may be related to human bipedalism. The genital and armpit regions also contain springy hairs which help diffuse body odors. The main components of human axillary odor are unsaturated or hydroxylated branched fatty acids with E-3-methylhex-2-enoic acid (E-3M2H) and 3-hydroxy-3-methylhexanoic acid (HMHA), sulfanylalkanols and particularly 3-methyl-3-sulfanylhexan-1-ol (3M3SH), and the odoriferous steroids androstenone (5α-androst-16-en-3-one) and androstenol (5α-androst-16-en-3α-ol).