Hacker News Reader

Comment by mallomarmeasle | Hacker News Reader

The article mentions that dry earwax is found in Asians, in comparison to the sticky form in Westerners. It does not mention the fascinating detail that this difference is determined by a single gene, which also influences underarm odor. http://udel.edu/~mcdonald/mythearwax.html https://en.wikipedia.org/wiki/ABCC11

View on HN

Because of this gene more than 95% of Chinese have very little body odor. Consequently, Chinese regard those with heavy body odor as ill, and name the illness 狐臭 ("fox stink" by transliteration). Those with heavy body odor are shamed by their peers. Few of Chinese know that almost everyone outside China, Korea and Japan shares this "illness", and deals with it daily with deodorants.

There are business implications too -- I remember an article years ago about Unilever or some similar company's ambitions to enter a virtually untapped Chinese deodorant market. I just tried to find what happened, and it seems that didn't work out: https://www.nytimes.com/2018/02/02/business/china-consumers-...

I wonder what other factors can contribute to the matter. Korean guy here. I swear that a decade ago, I would not get significantly stinky as I got sweaty. These days, I am totally stinky after a basketball game. My feet are so stinky after a day in shoes. My armpits are crazy stinky after a day of work, they totally were not this stinky a few years ago.

Yes, I do not have conclusive data on the matter. It's all anecdotal and non-scientific. But I swear it's true. I swear it.

How old are you? I heard (I am not sure) that the dominant allele of this gene (the stinky one) only shows its effect after teenage years.

Just hit 36. So... a decade ago, I was 26?

Well, my hypothesis is wrong then.

up till now, reading about the dry vs wet earwax, I had always understood the smell to be determined by the type of bacteria feeding on urea in the sweat. The urea contains chemical energy, but is expelled nonetheless by the human body to get rid of the nitrogen. I also clearly remember knowing about this mechanism and reading on practically all the deodorant bottles (perhaps 5 years ago) brand or no brand that it contained perfume, other things and ... urea! so basically pretty smell that evaporates over time, while feeding the stinking bacteria so you'd spray again.

Then I noticed urea dissappearing from the deodorant bottles.

According to this theory the smell of sweat is really determined by the breakdown products the bacteria release, so that would imply killing the current colony and applying an odorless colony.

Perhaps people with smelly sweat are just alternating faster between colonies by having periods of working out, and periods of not working out which causes the occasional good colony to die and get replaced with a smelly one? Perhaps people who smell less have a more regular colony feeding pattern?

Underarm odor is largely determined by bacterial breakdown products of fatty acids, steroids, and other aliphatics into odorous compounds such as smaller-chain acids. Urea plays no role that I know of. See https://en.wikipedia.org/wiki/Biochemistry_of_body_odor

I could perfectly be wrong about the odour being a breakdown product of the urea itself, but I thought the urea was a major energy source for the bacteria... is that still correct or are the other species you mention more energetic or available?

I think urea will be in sweat mainly in the case of damaged kidneys, not under normal conditions. Not sure about that though.

https://www.ncbi.nlm.nih.gov/pubmed/12817713/

Is there some sort of Western habit that you acquired? Maybe you changed your diet, the fabric of your shirts and socks, or your soap/shampoo habits.

And thus obeys good old Mendelian inheritance rules perfectly!

Reply on news.ycombinator.com