Of all the human scents, underarm or axillary odor has been the most studied due to the billion dollar market that exists for deodorants and antiperspirants. The identification of odoriferous compounds generated by the action of micro-organisms, mainly corynebacteria, on apocrine secretion is still an area of intense activity with the ultimate aim of unravelling the secrets of the underarm odor.
There has been a lot of controversy as to exactly which compounds are responsible for the characteristic axilla odor. Reviews by Labows (1998) and Gower (1989) containing extensive lists of references on the subject, suggest that the characteristic odor in the underarm is due to the presence of the volatile steroids 5-α-androst-16-en-3-ol (androstenol), 5-α-androst-16-en-3-one (androstenone) and 4,16-androstadien-3-one (androstadienone) as well as isovaleric acid.
Recently the topic of underarm odor received the attention of the world press in headline like "Scientists find chemical clue to body odor" (New York Times, August 1990). "Key ingredient in the armpit odor sniffed out" (Washington Post, August 1990), "Science sniffs out culprit in damp case" (Herald Tribune, European Edition, August 1990), and "Stink-tank scientist reports body-odor breakthrough" (The Japan Times, August 1990, referring to the work of George Preti of the Monell Centre). The new finding proposed that underarm odor was mainly due to volatile C6-C11 straight chain or branched unsaturated acids and that the major contributor to the characteristic odor with a high odor impact was (E)-3-methyl-2-hexenoic acid. The (Z)-isomer, found at one tenth the concentration of the (E)-isomer, also had a high odor impact, but not the underarm odor quality.
