Cerumen–Earwax

Earwax, also known by the medical term cerumen, is a yellowish waxy substance secreted in the ear canal of humans and many other mammals. It protects the skin of the human ear canal, assists in cleaning and lubrication, and also provides some protection from bacteria, fungi, insects and water. Excess or impacted cerumen can press against the eardrum and/or occlude the external auditory canal and impair hearing.

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.

There are two distinct genetically determined types of earwax: the wet type, which is dominant, and the dry type, which is recessive. East Asians and Native Americans are more likely to have the dry type of cerumen (grey and flaky), whereas Caucasians and Africans 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. 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.” In addition to affecting cerumen type, this mutation also reduces sweat production.

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