What does earwax say about your health?

Earwax is probably the last thing you want to talk about in a pleasant conversation, with its orange and sticky texture. However, it is increasingly attracting the attention of scientists who want to learn about metabolic disorders such as cancer, heart disease and type 2 diabetes.

The scientific name for this sticky substance is cerumen and it is a mixture of secretions from the two types of glands that line the external ear canal, the ceruminous and sebaceous glands.

This resulting mixture combines with hair, dead skin cells and other body debris to reach its familiar waxy consistency.

This substance, which is formed in the ear, is transported towards the outer ear by a system that can be likened to a conveyor belt, and it clings to the skin cells and moves at a speed of approximately one-twentieth of a millimeter every day.

The exact function of earwax is still unknown, but its most likely function is to keep the ear canal clean and moist. It also acts as an effective trap to prevent unwanted visitors such as bacteria, fungi, and even insects from entering our heads.

Earwax, the ugly-looking substance that is often confused with other bodily fluids, hasn’t received much research attention, but that’s starting to change thanks to some surprising scientific discoveries.

Earwax can provide a lot of important and unimportant information about a person.

For example, the vast majority of people of European or African descent have "wet" earwax, which is yellow-orange and sticky, but 95 percent of people of East Asian descent have "dry", gray earwax.

This difference is under the control of a gene called ABCC11.

The same gene also plays a role in underarm odor, and about 2 percent of people with a certain version of this gene (who often have dry earwax) may have no underarm odor at all.

But the most interesting discoveries concern what earwax can tell us about health.

In 1971, Nicholas L. Petrakis of the University of California discovered that American, African-American, and German women with wet earwax had a breast cancer death rate nearly four times higher than Japanese and Taiwanese women with dry earwax.

In 2010, Tokyo Institute of Technology researchers found that Japanese women with breast cancer were 77 percent more likely to have the wet earwax gene than healthy women.

This finding is controversial, though; large-scale studies in Germany, Australia and Italy found no difference in breast cancer risk between the two types of earwax, although the number of people with dry earwax in these countries is quite low.

A NEW ERA IN DIAGNOSTICS

There are also stronger connections between some diseases and substances found in earwax.

In rare genetic disorders such as maple syrup urine disease, urine and blood smell distinctly sweet. The molecule that causes this odor, called sotolon, can also be detected in patients' earwax.

So, this disease can only be diagnosed by taking a sample of earwax.

"That sweet smell coming from a newborn's ear can indicate the presence of disease within 12 hours," says Rabi Ann Musah, an environmental chemist at Louisiana State University.

Covid-19 can also sometimes be detected in earwax. It can also be used to tell whether a person has type 1 or type 2 diabetes.

Early research suggests that some heart diseases can also be detected from earwax, but blood tests are currently more practical for such conditions.

Another condition Musah deals with is Ménière's disease, which causes dizziness, nausea and hearing loss.

Musah and his team discovered that individuals with Ménière's disease have significantly lower levels of three different fatty acids in their earwax than healthy individuals. This finding could enable rapid diagnosis of the disease.

"Ear wax holds great promise, especially for rare and difficult-to-diagnose diseases," Musah said, adding that ear wax could be a new way to diagnose diseases that take a long time to diagnose through blood, urine or cerebrospinal fluid.

WHY EAR WAX?

So what makes earwax so important? Answer: Metabolism.

"Many diseases are of metabolic origin. For example, diabetes, cancer, Parkinson's and Alzheimer's," according to Nelson Roberto Antoniosi Filho, a chemistry professor at the Federal University of Goiás in Brazil.

In these diseases, the mitochondria within the cell begin to work differently; they produce new substances or stop producing some of them.

Earwax reflects these chemical changes better than other body fluids because it accumulates slowly, creating a "metabolic archive" over time.

Bruce Kimball, a chemical ecologist at the Monell Center for Chemical Senses in Philadelphia, USA, also supports this idea:

"Earwax accumulates over time, creating an ideal environment for capturing long-term changes in metabolism."

CANCER DIAGNOSIS WITH 'CERUMENOGRAM'

Using this insight, Antoniosi Filho and his team developed a diagnostic tool called the "cerumenogram."

In a 2019 study, earwax samples were taken from 52 cancer patients diagnosed with lymphoma, carcinoma, or leukemia and 50 healthy individuals.

Volatile organic compounds (VOCs) were analyzed in these samples and a "cancer trace" of 27 molecules was discovered.

As a result, thanks to these 27 molecules, it was possible to predict with 100 percent accuracy whether a person had cancer or not.

Since the molecules originate from the common metabolism of cancer cells, it could not be distinguished which type of cancer it was.

The research group is now focusing on a smaller number of molecules that are produced solely by the metabolism of cancer cells.

According to new unpublished studies, this method can also detect precancerous cell changes.

"Many types of cancer have a treatment success rate of up to 90 percent when diagnosed in the first stage. Therefore, diagnosing pre-cancerous stages can further increase the success rate," says Antoniosi Filho.

Researchers are investigating whether early signs of neurodegenerative diseases such as Parkinson's and Alzheimer's can also be detected from earwax.

Amaral Carvalho Hospital in Brazil has begun using the cerumenogram as a diagnostic and monitoring tool for cancer treatment.

Musah aims to develop a home test kit that can be used to diagnose Ménière's disease, just like Covid-19 tests.

A NEW MEDICAL MATERIAL

Musah says we need to better understand the chemical makeup of normal, healthy earwax.

But his goal is for earwax to one day be routinely analyzed in hospitals, just like blood.

“Earwax, which is very rich in fat, is an excellent test material for diseases related to fat metabolism disorders,” Musah adds.

This view is supported by Prof. Perdita Barran, a chemist and mass spectrometrist at the University of Manchester, who does not work specifically on earwax but analyses biological molecules:

"The compounds you find in blood are generally water-soluble. But earwax is oil-based, so it can be a unique proxy for seeing the initial changes in oils."