JK is the reason for the B.O. - 美容整形・美容外科｜船橋中央&青山セレスクリニック　美容整形・美容外科｜船橋中央&青山セレスクリニック

JK is a bacteria, formally known as Corynebacterium jeikeium. This skin-resident bacterium plays a major role in producing the distinctive odor associated with body odor, commonly referred to as “BO.”

Mechanism of Body Odor

So why does body odor, medically referred to as bromhidrosis, produce such a unique smell? Let’s delve into the mechanism behind it.

①When the sympathetic nervous system is stimulated, and sweat is secreted, it includes sweat from the apocrine sweat glands located in areas like the armpits. There are two types of sweat glands in the human body: the apocrine sweat glands mentioned before, and the eccrine sweat glands, which are spread throughout the skin and primarily help to regulate body temperature. Eccrine sweat glands do not directly contribute to body odor.

②Individuals with bromhidrosis have higher levels of N-acetyl-5-methylornithine (or compounds similar to it) in their apocrine sweat.

③N-acetyl-5-methylornithine is broken down by skin bacteria such as JK bacteria, resulting in the production of 3-methyl-2-hexenoic acid (TMHA), which is a major contributor to body odor.

About 3-Methyl-2-Hexenoic Acid (TMHA)

TMHA is an unsaturated short-chain fatty acid with the chemical formula C7H12O2. The only instance in which TMHA plays a role in our lives is in creating the smell associated with goats. In other words, the smell of goats and body odor are essentially the same. Body odor is often compared to the smell of rotten cheese, but this is a misconception. The smell of rotten cheese is due to isovaleric acid, which is a different chemical substance.

Can Eliminating JK Bacteria Cure BO?

While JK bacteria, a type of skin resident bacterium, is deeply involved in body odor, it cannot be eliminated as it is a commensal bacterium. While it is possible to temporarily reduce the number of bacteria on the skin through bathing or showering, bacteria can survive deep within the skin or inside hair follicles and will start to multiply rapidly once conditions become favorable again.

Originally, All Humans Had Body Odor

The substance N-acetyl-5-methylornithine in apocrine sweat is a key factor in the development of body odor. Anthropologically speaking, a mutation from 538G to 538A in the ABCC11 gene resulted in the cessation of production of this substance. Please refer to a previous blog for more details on the genetics of body odor.

Historically, it is believed that all humans initially had the GG genotype (associated with wet earwax and body odor). However, at some point, the 538G→538A( ※)mutation occurred, giving rise to individuals with the AA genotype, associated with dry earwax and a lack of body odor. This mutation spread over time, particularly in certain regions and among East Asian populations. The exact timing and reasons behind the emergence and spread of this mutation are not fully understood, but some theories suggest that it may have been advantageous in cold climates or specific ecosystem(s.

(※)The 538G→538A notation refers to a nucleotide change at position 538 in the ABCC11 gene, where guanine (G) is replaced by adenine (A).

In Conclusion

While JK bacteria are heavily involved in body odor, they cannot be eliminated. Since genetic factors play a significant role in the development of body odor, if you are concerned about it, it is recommended that you consult a specialist, such as a dermatologist or a cosmetic surgeon.

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