The intensity of axillary odor and the type of cerumen that people have are interrelated traits, since they share elements between them, such as their transporter in the membranes of the cells where these traits are manifested.
Earwax type / Armpit odor
Cerumen is a normal secretion of the ceruminous and sebaceous glands of the outer third of the external auditory canal. It is composed of glycopeptides, lipids, hyaluronic acid, sialic acid, lysosomal enzymes and immunoglobulins.
Earwax exerts a protective effect by maintaining an acidic environment (pH 5.2 to 7.0) in the ear canal, while lubricating the canal, protecting the ear from infection and providing a barrier against insects and water. Earwax is usually expelled from the ear canal spontaneously through the natural movement of the jaw.
Two types of cerumen occur in humans: the wet type, with brownish, sticky cerumen, and the dry type, with absent or reduced ceruminous secretion. The wet type is completely dominant to the dry type, and is very common in populations of European and African origin (~95% and ~100%, respectively). In contrast, the dry type is frequently observed in East Asian populations, with the prevalence of wet cerumen being ~15% in Japan, ~5% in Korea, and ~10% among the Chinese.
An association between axillary odor and wet-type cerumen was first identified approximately 70 years ago. Since then, attempts have been made to establish associations between the two traits by studying the regulators of each trait. It is in the apocrine and/or eccrine glands of the human body where odor is produced, especially the axillary and pubic apocrine glands.
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Genes analyzed
Bibliography
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Prokop-Prigge KA, Mansfield CJ, Parker MR, Thaler E, Grice EA, Wysocki CJ, et al. Ethnic/racial and genetic influences on cerumen odorant profiles. J Chem Ecol, 2015; 41(1):67–74.
Ohashi J, Naka I, Tsuchiya N. The Impact of Natural Selection on an ABCC11 SNP Determining Earwax Type. Mol Biol Evol, 2011; 28(1):849–57.
Martin A, Saathoff M, Kuhn F, Max H, Terstegen L, Natsch A. A functional ABCC11 allele is essential in the biochemical formation of human axillary odor. J Invest Dermatol, 2010; 130(2):529–40.
Harker M, Carvell A-M, Marti VPJ, Riazanskaia S, Kelso H, Taylor D, et al. Functional characterisation of a SNP in the ABCC11 allele - effects on axillary skin metabolism, odour generation and associated behaviours. J Dermatol Sci, 2014; 73(1):23–30.
