What this means

ABCC11 is a membrane transporter expressed in the ceruminous (earwax) and apocrine sweat glands. A single G→A change (rs17822931) results in a non-functional transporter, which produces dry, crumbly earwax and dramatically reduces the production of the precursor molecules that underarm bacteria turn into body odour. This is one of the few single SNPs in the human genome that produces a near-Mendelian visible trait: one variant cleanly explains the difference.

ABCC11 is a tiny molecular pump in your ear and underarm glands. One DNA change switches the pump off, and the result is dry, flaky earwax plus very little of the stuff your underarm bacteria need to make body odour. This is one of the rare cases where a single DNA change really does cleanly determine a visible everyday trait — wet versus dry earwax, and a normal versus a barely-there underarm smell.

Caveats

• The wet allele is dominant, so one C copy usually means wet earwax.
• The dry allele is much more common in East Asian populations than elsewhere.
• Reduced odour does not mean no odour — sweat composition still varies between people.
• This is genuinely one trait, not a proxy for anything medical.

References

• Yoshiura et al. — A SNP in the ABCC11 gene is the determinant of human earwax type (Nature Genetics, 2006)
• Martin et al. — A functional ABCC11 allele is essential in the biochemical formation of human axillary odor (Journal of Investigative Dermatology, 2010)