Where Does Earwax Come From? A Look at the Genetic Basis of Wet Earwax and Dry Earwax

What is Earwax?

According to the American Hearing Research Foundation, earwax is a “product of the ear …made by wax glands in the external ear canal.” It is a waxy substance that can vary in color (from yellowish to brown or even grey), amount, and consistency (soft, viscous, dry, and wet, etc). Earwax, also known as cerumen, functions as a protector of the internal ear canal, and as a lubricator. It is also believed to have antifungal and antibacterial properties. On the downside, having excess earwax in our ears can retain bacteria and lead to infection which may cause pain, and/or itching. And so earwax removal becomes necessary.

Where does Earwax Come From?

Earwax production has a genetic basis. In fact, there are two types of earwax: wet and dry, which are inherited. People with Asian and Native American ancestors tend to have the dry type (grey and flaky) while Caucasians and African Americans tend to have the wet type (moist, yellowish to brown). The lipid (fat) content is different in both types of earwax. Dry wax has about 20% fat while wet wax has nearly 50% lipid content (Burkhart et al, 2000).

Wet Earwax vs. Dry Earwax

The difference between dry and wet earwax has a genetic basis. Earwax type is perfect example of a how a trait can be determined by the difference in a single base (nucleotide). Dr. Koh-ichiro Yoshiura, from the Department of Human Genetics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan, reports, in a study published in the prestigious journal Nature, that a single nucleotide polymorphism (SNP) is responsible for the difference between dry and wet wax.

According to this study, the ABCC11 gene is responsible for the determination of earwax type (wet or dry). The nucleotide (base) 538 can be either Adenine (A) or Guanidine (G). The genotype AA leads to the dry earwax phenotype, while the combinations GA and GG lead to the wet type of earwax. The dry-earwax gene is recessive, meaning both parents must pass a copy to their children for the phenotype to manifest, while the wet-earwax allele is dominant. In this situation having only one copy of the gene will be enough for a child to inherit the wet type of earwax.

Sources:

Burkhart et al, 2000. Burkhart CN et al. In pursuit of ceruminolytic agents: a study of earwax composition. American Journal of Otol. 21(2):157-60.