Sebaceous origins of human odor

The compounds that make up human body odor have been catalogued by researchers in many fields. Yet few are aware of exactly where these molecules come from. Volatile body-odor compounds are often cited as being produced primarily via microbial activity from precursors in sweat. While this is a source of many human volatiles, here we synthesize data showing that some of the most distinctive and abundant components of human odor instead originate from precursors in sebum, via reactions that do not involve the skin microbiome. We also review the unique biochemistry of human sebaceous glands and discuss evolutionary hypotheses that may partly explain why human sebum is so unique. Finally, we discuss how sebum-derived volatiles intersect with human health and disease, for example, via attraction of disease-vector mosquitoes or use in medical diagnostics. Our review draws insights from multiple fields, which together provide surprising clarity on some of the proximate and ultimate mechanisms underlying the distinctive composition of human odor.