The weather is fine these last days, and it is unusually hot here in Belgium. I carry a deodorant in my handbag, for nothing is as unpleasant as a sweaty body odor. Especially in this weather, we Europeans sweat a lot. Thinking about the humid climate of Japan, a good deodorant only seems indispensable. Nevertheless, more than once I read that deodorants can hardly be found in Japan, or at least there is very limited choice. Why do Japanese not need to use deodorants?
Apparently it has to do with genetics. Wikipedia tells me that MHC, or major histocompatibility complex molecules, influence body odor. In our armpits, two different kinds of glands create sweat, eccrine and apocrine glands. Eccrine glands can be found all over the body, while apocrine glands develop during puberty in certain locations of the body, like armpits, genitalia, eyelids, breast etc. How much of the latter one possesses, is influenced by the ABCC11 gene, a gene that also determines the type of earwax a person has. Most of the world’s population, like Europeans and Africans, have wet and sticky earwax and more ceruminous apocrine sweat glands, and are therefore more prone to body odor. Earwax type is a Mendelian trait wherein the wet phenotype is the dominant one. So, most people around the world have wet earwax.
East Asians on the other hand (80 to 95% of Chinese, Korean and Japanese) are said to have dry earwax and fewer apocrine sweat glands. The ABCC11 gene does not function in the following way that it does not produce the protein that is needed in apocrine glands to attract bacteria. As a result, there is no secretion of the odorant compounds that create body odor.
Sometimes the observation that East Asians do not excrete body odor is explained as “having undeveloped sweat glands” or “lack of sweat glands in the armpits”, which is not true at all. On the contrary, recent research showed that East Asians possess traits that are the result of a gene mutation (more specifically of the gene EDAR) about 35,000 ago. These traits are: thicker hair shafts, smaller breasts, characteristically identified teeth – and more sweat glands. During the time of mutation, these people could be found in the warm and humid climate of central China, where extra sweat glands would have been advantageous. Another theory claims that sexual selection was the cause of the mutation. Not that sweating armpits were very sexy at that time, but the thick hair and the smaller breasts are likely to have been more attractive.
The fact that Japanese people sweat just as much as we do (or even more, due to more sweating glands) can be observed in shops and advertisement. Instead of preventing the smell, most products are developed to reduce sweating. For example in the following ads:
– NY Times, 14 feb 2013 “East Asian Physical Traits Linked to 35,000-Year-Old Mutation”
– The Guardian, 14 feb 2013, “Are you wasting money on deodorant? The answer can be found in your ears”
– site Natural Height Growth
– blog She in China
– site The Straight Dope
– site Livescience
– blog Robert Lindsay
– Ishikawa, Toshihisa, Yu Toyoda, Koh-ichiro Yoshiura, and Norio Niikawa. “Pharmacogenetics of Human ABC Transporter ABCC11: New Insights into Apocrine Gland Growth and Metabolite Secretion.” 110 学術雑誌論文 (January 2, 2013). link pdf
– credits pictures: 1. own picture 2. out of science article mentioned here above 3, 4, 5. from commercial sites