Human physiological variation reveals how genetics have adapted populations to different environments. Among these differences are variations in bodily functions, such as sweating and the production of body odor. While sweating is universal, the presence or absence of noticeable odor shows significant global variation. This difference is due to specific biological and genetic factors, not hygiene or diet. This article explores the underlying mechanisms of human sweat and the genetic factor that determines the presence or absence of underarm body odor, especially within East Asian populations, including Koreans.
The Biology of Human Sweating
All humans possess millions of sweat glands, primarily tasked with regulating body temperature. These glands fall into two main categories: eccrine and apocrine. Eccrine glands are the most numerous, covering nearly the entire body surface, and are responsible for thermoregulation. Eccrine sweat is largely composed of water and salt, and its evaporation provides a cooling effect. This type of sweat is essentially odorless due to its simple composition.
Apocrine glands are concentrated primarily in the armpits and groin area, opening into hair follicles. Active only after puberty, they produce a thicker sweat rich in lipids, proteins, and steroids. This apocrine secretion is initially odorless, but it serves as a nutrient-rich substrate for skin bacteria. When bacteria metabolize these compounds, they produce volatile organic compounds, which are the source of body odor.
The Role of the ABCC11 Gene
The variation in body odor is attributed to the ABCC11 gene (ATP-binding cassette transporter sub-family C member 11). This gene provides instructions for a protein that acts as a transporter, moving molecules across cell membranes in certain glands. A single-nucleotide polymorphism—a change from guanine (G) to adenine (A)—results in a non-functional version of the ABCC11 protein.
Individuals who inherit two copies of this variant (the AA genotype) produce a non-functional transporter. This genetic change significantly alters apocrine sweat composition by preventing the secretion of odor-producing precursor molecules. The non-functional ABCC11 gene is highly prevalent in East Asian populations, including Koreans, often reaching 80% to 95% frequency. This contrasts sharply with African and European populations, where the ancestral G allele, associated with functional sweat secretion and odor, is the norm.
The ABCC11 gene variant also determines the type of earwax a person produces. The ancestral G allele is associated with “wet” and sticky earwax, common globally. Conversely, the non-functional A allele, common in East Asians, results in “dry,” flaky earwax. This dry earwax phenotype is a visible indicator of the genotype associated with reduced body odor. The mutation may have offered an adaptive advantage in colder climates by reducing sweat gland activity, thereby helping to preserve body heat.
Genetic Influence on Body Odor
The non-functional ABCC11 gene variant results in a significant reduction in underarm body odor. Since the variant prevents the necessary fatty and protein components from being transported into the apocrine sweat, the bacteria on the skin’s surface are effectively starved of their primary food source. With less substrate to metabolize, the production of volatile organic compounds—the source of the smell—is dramatically reduced or absent.
This difference is purely a genetic trait, independent of personal hygiene practices. Research has shown that individuals with the non-odor-producing genotype (AA) have a different microbial community in their armpits compared to those with the odor-producing genotype (GG or GA). The presence of the functional ABCC11 protein (G allele) encourages the growth of bacteria like Corynebacterium, which are efficient at creating strong, characteristic body odors. People with the non-functional ABCC11 variant tend to have a less diverse bacterial composition, resulting in minimal or neutral odors.