Fear Of Stink: A Century In The Making
Jan22

Fear Of Stink: A Century In The Making

Lurking among us are foolish folks who fork out cash for deodorants even though their armpits don’t smell. This is the take-home message of an article in the Journal of Investigative Dermatology that’s been making the rounds of science news sites and blogs. It’s a fun study, but the results aren’t really that surprising. Researchers have known for years that some people in Europe (2% of the population) and most people in China, Japan, and Korea are fortunate enough to have two copies of a recessive gene that makes their armpits relative* stink-free zones. That’s because the gene codes for a protein involved in transporting molecules out of special sweat glands that appear in your armpits at puberty. These stink-producing glands are called apocrine glands, and they differ from eccrine glands, which are found all over your body and produce the salty fluid we commonly associate with sweat and body temperature regulation. Apocrine glands typically excrete all manner of waxy molecules that armpit bacteria love to feast on. It’s the leftover, metabolized molecules, such as trans-3-methyl-2-hexanoic acid, which give many human bodies that oh-so-ripe odor. Because the difference between stinky and stink-free folks is a gene involved in transporting armpit molecules, it’s pretty likely that people without body odor have a dysfunctional transporter. Although that’s not yet been proven, it’s a reasonable theory. For example, people with odorless armpits also produce a dry white earwax, instead of a yellowish wet version. Presumably, the transport machinery that isn’t exporting bacteria food in the armpit isn’t exporting a yellowish fluid in the ears either. What’s really new in the article is simply the observation that among the 2% of folks in the UK who probably don’t need to apply deodorant, 78% still do. OK, so why is this not really surprising? For one, the UK is dominated by people who have stinky armpits. If you are stink-free, it’s because you have two copies of the recessive, odorless allele of the gene, which behaves in a rather Mendelian fashion, says Ian Day, the University of Bristol researcher who led the study. Being stink-free is rare in the UK, so both parents of an odorless child are probably heterozygous. That means they carry one stinky allele of the gene and one stink-free allele, but they are stinky themselves. Statistically, only one quarter of these parents’ kids will be stink-free. So you can imagine that stinky parents are likely to give their awkward teenagers deodorants in anticipation of that day when their bodies start announcing adulthood. And they probably do it prematurely, so that their teenagers don’t suffer ridicule from other, more well-prepared schoolmates....

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