28 April 2025, Jasmin Fox-Skelly, BC
From Alzheimer's to cancer, earwax can contain valuable indicators to a person's health. Now scientists are analysing its chemistry in the hope of finding new ways of diagnosing diseases.
It's orange, it's sticky, and it's probably the last thing you want to talk about in polite conversation. Yet earwax is increasingly attracting the attention of scientists, who want to use it to learn more about diseases and conditions like cancer, heart disease, and metabolic disorders such as type 2 diabetes.
The proper name for the gloopy stuff is cerumen, and it's a mix of secretions from two types of glands that line the outer ear canal; the ceruminous and sebaceous glands. The resulting goo is mixed with hair, dead skin flakes, and other bodily debris until it reaches the waxy consistency we all know and try our best not to think about.
Once formed in the ear canal, the substance is transported by a kind of conveyer belt mechanism, clinging on to skin cells as they travel from the inside of the ear to the outside – which they do at a speed of approximately one 20th of a millimetre every day.
The primary purpose of earwax is debated, but the most likely function is to keep the ear canal clean and lubricated. However, it also serves as an effective trap, preventing bacteria, fungi and other unwelcome guests such as insects from finding their way into our heads. So far, so gross. And yet, possibly due to its unpalatable appearance, earwax has been somewhat overlooked by researchers when it comes to bodily secretions.
That's now starting to change, however, thanks to a slew of surprising scientific discoveries. The first is that a person's earwax can actually convey a surprising amount of information about them – both trivial and important.
For example, the vast majority of people of European or African descent have wet earwax, which is yellow or orange in colour and sticky. However, 95% of East Asian people have dry earwax, which is grey and non-sticky. The gene responsible for producing either wet or dry earwax is called ABCC11, which also happens to be responsible for whether a person has smelly armpits.
Around 2% of people – mostly those in the dry earwax category – have a version of this gene which means their armpits have no odour.
However, perhaps the most useful earwax-related discoveries relate to what the sticky stuff in our ears can reveal about our health.
Important clues
In 1971, Nicholas L Petrakis, a professor of medicine at University of California, San Francisco, found that Caucasian, African-American and German women in the USA, who all had "wet earwax", had an approximately four-fold higher chance of dying from breast cancer than Japanese and Taiwanese women with "dry" earwax.
More recently in 2010, researchers from the Tokyo Institute of Technology took blood samples from 270 female patients with invasive breast cancer, and 273 female volunteers who acted as controls. They found that Japanese women with breast cancer were up to 77% more likely to have the gene coding for wet earwax than healthy volunteers.
Nevertheless, the finding remains controversial, and large scale studies in Germany, Australia and Italy have found no difference in breast cancer risk between people with wet and dry earwax, although the number of people in these countries with dry ear wax is very small.
What is more established is the link between some systemic illnesses and the substances found in earwax. Take maple syrup urine disease, a rare genetic disorder that prevents the body from breaking down certain amino acids found in food. This leads to a buildup of volatile compounds in the blood and urine, giving urine the distinctive odour of maple syrup.
The molecule responsible for the sweet-smelling wee is sotolone, and it can be found in the earwax of people with the condition. This means the condition could be diagnosed through simply swabbing someone's ears, a much simpler and cheaper process than doing a genetic test. Although such a test may not even be necessary.
"The earwax literally smells like maple syrup, so within 12 hours of the birth of the baby, when you smell this distinct and lovely smell it tells you that they have this inborn error of metabolism," says Rabi Ann Musah, an environmental chemist at Louisiana State University.
Covid-19 can also sometimes be detected in earwax, and a person's earwax can also tell you whether they have type 1 or type 2 diabetes. Early work has suggested that you can tell if someone has a certain form of heart disease from their earwax, although it's still easier to diagnose this condition from blood tests.
There's also Ménière's disease, an inner ear condition that causes people to experience vertigo and hearing loss. "The symptoms can be very debilitating," says Musah. "They include severe nausea and vertigo. It becomes impossible to drive, or to go places accompanied. You eventually suffer complete hearing loss in the ear that is afflicted."
Musah recently led a team which discovered that the earwax of patients with Ménière's disease has lower levels of three fatty acids than that of healthy controls. This is the first time anyone has found a biomarker for the condition, which is usually diagnosed by excluding everything else – a process which can take years. The finding raises the hope that doctors could use earwax to diagnose this condition more quickly in the future.
"Our interest in earwax as a reporter of disease is directed at those illnesses that are very difficult to diagnose using typical biological fluids like blood and urine or cerebral spinal fluid, and which take a long time to diagnose because they're rare," says Musah.
But what is it about earwax that makes it such a treasure trove of health information? The key, it turns out, is down to the waxy secretions' ability to reflect the inner chemical reactions taking place inside the body – a person's metabolism.
The researchers identified 27 compounds in earwax that served as a kind of "fingerprint" for cancer diagnosis "Many diseases in living organisms are metabolic," says Nelson Roberto Antoniosi Filho, a professor of chemistry at the Federal University of Goiás in Brazil, who lists diabetes, cancer, Parkinson's, and Alzheimer's disease as examples. "In these cases, mitochondria – the cell organelles responsible for converting lipids, carbohydrates, and proteins into energy – begin to function differently to those in healthy cells. They start to produce different chemical substances and may even stop producing others."
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