Earwax - Physiology

Physiology

Cerumen is produced in the outer third of the cartilaginous portion of the human ear canal. It is a mixture of viscous secretions from sebaceous glands and less-viscous ones from modified apocrine sweat glands. The primary components of earwax are shed layers of skin, with 60% of the earwax consisting of keratin, 12–20% saturated and unsaturated long-chain fatty acids, alcohols, squalene and 6–9% cholesterol.

Fear, stress and anxiety result in increased production of earwax from the ceruminous glands.

There are two distinct genetically determined types of earwax: the wet type, which is dominant, and the dry type, which is recessive. While Asians and Native Americans are more likely to have the dry type of cerumen (gray and flaky), African and European people are more likely to have the wet type (honey-brown to dark-brown and moist). Cerumen type has been used by anthropologists to track human migratory patterns, such as those of the Inuit. In Japan, wet-type earwax is more prevalent among the Ainu, in contrast to country's Yamato majority. The consistency of wet type earwax is due to the higher concentration of lipid and pigment granules (50% lipid) in the substance than the dry type (30% lipid).

The difference in cerumen type has been tracked to a single base change (a single nucleotide polymorphism) in a gene known as "ATP-binding cassette C11 gene." Dry-type individuals are homozygous for adenine whereas wet-type requires at least one guanine. Wet-type earwax is associated with armpit odor, which is increased by sweat production. The researchers conjecture that the reduction in sweat or body odor was beneficial to the ancestors of East Asians and Native Americans who are thought to have lived in cold climates.