In the past, Hearing International reviewed the racial implications of cerumen as well as how it is removed in various parts of the world. So when the story broke about the use of earwax in personal identification, it was a discussion that we could not resist. Recently scientists from the Monell Center in Philadelphia, PA (USA) have used analytical organic chemistry to identify the presence of odor-producing chemical compounds in human cerumen. Before we go too far into this discussion, let’s consider some well-known facts about earwax.
First of all, earwax or cerumen is a yellowish, waxy substance secreted in the ear canal of humans and 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 (block) the external auditory canal or hearing aids, potentially hindering hearing.
Cerumen is produced in the outer third of the cartilaginous portion of the ear canal. It is a mixture of viscous secretions from sebaceous glands and less-viscous secretions from modified apocrine sweat glands. The primary components of cerumen are shed layers of skin, with 60% of the earwax consisting of keratin (12%–20% saturated and unsaturated long-chain fatty acids) alcohols, squalene (a lipid produced by human skin cells, making up approximately 10% of our sebum. On the skin’s surface it acts as a barrier, both protecting the skin from moisture loss and providing a shield for the body from environmental toxins) and 6%–9% cholesterol.
type of cerumen (gray and flaky), people of African and European descent 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-type earwax being more prevalent among Japan’s Ainu population, in contrast to that country’s Yamato majority. The consistency of the wet type of earwax is thought to be caused by the higher concentration of lipid and pigment granules (50% lipid) in the substance than in the dry type (30% lipid). A few weeks go at Hearing International, we discussed the use of Whale cerumen to track the migratory patters of those sea mammals and the content of the ocean during their lifetimes. So it’s not just humans whose cerumen can reveal where have come from!
A Neglected Body Secretion?
Scientists from many disciplines work together at the Monell Center in Philadelphia to gain understanding of the mechanisms and functions of taste and smell and to define the broad significance of these senses in human health and disease. The Center is the world’s only independent, non-profit scientific institute dedicated to basic research on taste and smell. Researchers from the Center have used analytical organic chemistry to identify the presence of odor-producing chemical compounds in human earwax. Further, they found that the amounts of these compounds differ between individuals of East Asian origin and Caucasians. The findings suggest that human earwax, an easily obtained bodily secretion, could be an overlooked source of personal information.
“Our previous research has shown that underarm odors can convey a great deal of information about an individual, including personal identity, gender, sexual orientation, and health status,” said study senior author George Preti, PhD, an organic chemist at Monell. “We think it possible that earwax may contain similar information.” Preti’s interest in earwax was piqued by the finding that a small change in a gene known as ABCC11 is related both to underarm odor production and also to whether a person has wet or dry earwax.
To determine if earwax has a characteristic odor, the researchers collected earwax from 16 healthy men: eight Caucasian and eight of East Asian descent. Each sample was placed into a vial, which was gently heated for 30 minutes to promote release of airborne molecules known as volatile organic compounds (VOCs), many of which are odorous. An absorbent device was then inserted through the vial’s cap to collect VOCs from the closed containers, and gas chromatography-mass spectrometry techniques were used to analyze the chemical compounds. The analysis revealed 12 VOCs that were consistently present in the earwax of all the men. However, the amount of VOCs varied as a function of the subject’s ethnic background, with Caucasians having greater amounts of 11 of the 12 VOCs than East Asians.
“In essence, we could obtain information about a person’s ethnicity simply by looking in his ears. While the types of odorants were similar, the amounts were very different,” said study lead author Katharine Prokop-Prigge, a Monell chemist. Click on Katharine’s picture for a great video of her research. The researchers suspect that the fatty nature of earwax makes it a likely repository for lipid-soluble odorants produced by certain diseases and by the environment. Prokop-Prigge points out that at least two odor-producing metabolic diseases (maple syrup urine disease and alkaptonuria) can be identified in earwax before they can be diagnosed using traditional techniques such as blood and urine analysis. “Odors in earwax may be able to tell us what a person has eaten and where they have been,” said Preti. “Earwax is a neglected body secretion whose potential as an information source has yet to be explored.”
In the future, it may be possible to determine where a person has been, how they smell, and even if they are gay by simply analyzing their cerumen. This offers a totally different perspective on Cerumen Removal!