Earwax type / body odor

A single change in the ABCC11 gene sets whether your earwax is wet or dry and how strong your underarm odor tends to be. It's one of the few traits decided by essentially one gene.

What this ABCC11 variant does

ABCC11 is a transporter that moves molecules out of cells, including in the ceruminous glands that make earwax and the apocrine glands in the armpit. This variant, 538G>A, changes a single amino acid, and the resulting protein is destroyed by the cell's quality control machinery before it ever reaches the membrane.

With no working transporter, earwax comes out dry and flaky rather than wet and sticky, and the apocrine glands secrete much less of the precursor molecules that skin bacteria convert into body odour. Odour is produced by bacteria acting on those secretions, so cutting off the supply is what reduces it.

How strong the evidence is

This is one of the cleanest genotype to phenotype relationships in common human variation, and it needs no statistics: two non-functional copies give dry earwax essentially without exception. The link to axillary odour is nearly as strong, and Japanese studies of axillary osmidrosis found that the wet-type genotypes are effectively a prerequisite for the condition, to the point that genotyping is used there as a marker.

ClinVar lists the variant under variation in apocrine gland secretion, axillary odour and colostrum secretion, reflecting that the same transporter operates in the breast.

Why this variant is a landmark in population genetics

The frequency difference across populations is among the largest known for a coding variant. In 1000 Genomes reference data, about 76% of East Asian-ancestry individuals carry two non-functional copies, against roughly 1.7% of European-ancestry and 0.07% of African-ancestry individuals, with South Asian samples in between.

A genome-wide scan for positive selection found the region around ABCC11 bears the signature of a selective sweep in East Asians, and this variant is the most plausible target. What that selection was for is not settled, which is a good example of a genuinely open question in human genetics sitting behind a trait people think of as trivial.

What this variant does not tell you

It does not decide whether you smell. Body odour also comes from eccrine sweat, skin and gut microbiome composition, diet, medication, hormones and hygiene, and people with two non-functional copies can still develop odour from those routes. What the variant removes is one major substrate supply, not the possibility of odour.

Nor does it say anything about earwax quantity, impaction or ear health, which are unrelated to the wet or dry distinction.

What each rs17822931 genotype means

rs17822931 has three possible genotypes: CC, CT and TT.

Wet earwax (rs17822931 CC). You have two copies of the common wet version of ABCC11, so your earwax tends to be sticky and moist. The same gene drives underarm sweat chemistry, so you're also more likely to have noticeable body odor (nothing washing can't handle).

Wet earwax (rs17822931 CT). You carry one wet and one dry copy of ABCC11. The wet version wins out, so your earwax is likely the sticky type and your body odor is in the typical range.

Dry earwax, low odor (rs17822931 TT). You have two copies of the dry version of ABCC11, so your earwax is the dry, flaky type. The same variant also means your underarms make less of the compounds behind body odor, so you probably have little to none. This pattern is common in East Asia.

Evidence & sources

Across global populations, about 5% of people carry two copies of this variant, and about 72% carry none.

Common questions

Does dry earwax mean I have no body odour? It means much less of the apocrine secretion that skin bacteria turn into underarm odour, which is why the association with axillary odour is so strong. It is not a guarantee: eccrine sweat, skin bacteria, diet and medication can still produce odour.

Why is dry earwax so common in East Asia? Because the non-functional version of ABCC11 reached high frequency there, in around 76% of East Asian-ancestry individuals as two copies, and the surrounding genomic region carries the signature of positive selection. What was being selected for is still unresolved.

Is wet earwax a problem? No. Wet earwax is the ancestral type and is the norm in most of the world. Neither type is healthier, and the only practical difference beyond texture is the association with underarm odour.

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