YOU can tell yourself you haven’t been too naughty over the festive season. You may even be able to convince others. But whether it’s an extra portion of Christmas pudding, too many glasses of wine or even the odd cigarette, the proof of your indulgences may be lurking somewhere altogether more surprising – inside your ears.
Earwax can easily be dismissed as a little gross and something to get rid of, but we are fast discovering that it is more than just another bodily secretion. All sorts of secrets about you are collected in it. With enough detailed probing of the stuff, says Katherine Prigge of fragrance company Symrise, based in Marlow, UK, it is possible that earwax could be used to reveal not only someone’s identity, “but information about where they’ve been, what they’ve eaten and what they were exposed to”. From drug tests to disease diagnosis, the potential of its unique chemical signature is starting to be put to good use. It may even give us answers about the lives of other animals who can’t tell us for themselves.
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More formally, the glop in your ears is called cerumen, and it is made up of the secretions of the – specialised sweat glands – and sebaceous glands in the outer ear canal. Most of these are waxy compounds, which clean the ear canal and protect it from drying out, as well as killing bacteria and trapping foreign bodies like dust and fungal spores. Mixed into that wax are bodily cast-offs like shed skin cells and hair, alongside potent antimicrobials and other chemicals.
It is these other chemicals – the leftovers of cellular processes and traces of substances you have been exposed to – that, we are now starting to realise, contain a surprising amount of intel about you.
For the past few years, Engy Shokry at the Federal University of Goiás in Goiânia, Brazil, and her colleagues have been doing some pioneering experiments to test whether earwax can be used as a forensic or diagnostic tool. As well as being able to extract plain old DNA from it, they have used earwax to detect and and
One advantage of earwax over other samples like blood or urine is that collection is more straightforward and less invasive. “Just asking a patient for a cotton swab in their ear is much easier than asking to draw blood,” says Shokry. To ensure they get enough, they ask that volunteers don’t clean inside their ears (a – earwax should just fall out naturally) for a week beforehand. “We can get 20 milligrams, which is more than enough for our tests,” she says. And earwax needs little, if any, processing to be analysed. “It takes around a tenth of the preparation time of other kinds of samples.”
Earwax factor
It has other advantages, too. “Because earwax builds up over time, you can look back and get more information,” says Prigge; blood and urine only give a “snapshot of what’s going on in your body at this moment.” In the lab, Shokry has shown that tests on earwax can detect drugs up to three months after they were taken, provided the patient hasn’t been meticulously Q-tipping. This means we can use it for both short and long-term monitoring of some substances, she says.
“One earplug was 50 centimetres long – and you can imagine the smell”
You don’t even need to extract compounds from the wax directly: valuable information can be gathered by smell alone. “It’s definitely not the most pleasant smell,” says Prigge, who spent years getting acquainted with it. “It’s kind of acidic and pungent. There are also some faecal notes to it… and a goat-like odour.”
We already knew that there are two types of earwax – and that which kind you have is linked to ethnicity (see “Divided by earwax“). But Prigge has also identified about a dozen different volatile compounds present in earwax at levels that – and since these substances make up smells, a person’s ancestry could be partly deciphered using the scent of their earwax.
These findings are just the tip of the iceberg in terms of what information the stuff may hold. Some of the most incredible discoveries have come not from humans, but from the giant plugs removed from whales. These help to transmit acoustic vibrations underwater, and are another ball of wax altogether. “We had one particular earplug that was 50 centimetres long and weighed about 2 pounds,” says Stephen Trumble, a marine mammal physiologist at Baylor University in Texas. “And you can imagine the smell.”
The wax plugs are often collected and kept in museums alongside bones and such because they are used to determine age. With whale ears largely sealed off from the outside, the earwax compacts over time into layers. “You can cut it in half and count the rings, like a tree,” Trumble says.
The other details Trumble and his colleagues can glean by carefully sampling and analysing the layers is astounding, ranging from DNA to hormones. In their most recent, as yet unpublished, work they looked at 20 earplugs with about 1100 layers between them and were able to connect high levels of stress hormones such as cortisol with historical whaling activity. “The data are kind of unprecedented,” he says. “To be able to show a tight correlation between 20th-century whaling and stress in whales – you could never ever in a million years do that without earplugs.”
Whales aren’t the only mammals whose ears offer clues to their past. In one experiment on cattle earwax, Shokry , a poison US farmers use against coyotes, and one that is hard to identify in other biological fluids, meaning diagnoses of accidental cattle poisoning are currently only made using symptoms and the animal’s history. She hopes this will improve diagnoses.
We hear ewe
Shokry has shown that changes in ewe earwax relate to pregnancy and lactation too. Since earwax requires no veterinary experience to collect, this could offer a simple, cheap way to check up on farm animals, and one that would be less stressful for them. Shokry is also soon to publish a study on spotting cancer using dog earwax.
But for all the promise earwax shows as a diagnostic tool, it could be some time before it reaches the clinic. We have centuries of data about what blood and urine samples should look like, but little on earwax, says Craig Wheelock at the Karolinska Institute in Sweden, who looks at molecular signatures of disease. “Earwax is an open book, so to speak – for good and bad.” And although careful analysis can tell us a lot about what someone has been up to, the sheer diversity in earwax makes it hard to know what anomalies look like. “Normalising it so that earwax is earwax is earwax will be a challenge,” Wheelock says.
That said, we have overcome similar challenges before. “We’ve been working this field for 15 years and we’ve done over 300 different types of sample,” says Mike Milburn at Metabolon, a firm based in North Carolina that profiles biological markers. In principle, there is no reason why you wouldn’t get a good representation of important biomarkers in earwax, he says.
But for now, any confidential information will stay archived in your ear where nobody can get at it. The perfect excuse for another brandy.
Divided by Earwax
Next time a lump of earwax falls out of your ear, what do you see: flaky, whitish-yellow stuff or sticky, orange-brown goop? The difference is down to a single gene: ABCC11.
Dry, flaky earwax is most common in people of East Asian descent. A change in just a single DNA base pair in the ABCC11 gene encodes for the “wet” kind, most often found in people of African or European descent. The difference isn’t just cosmetic. The : people with dry earwax stink less.
And we are just beginning to understand what the ABCC11 protein does in the body. Some forms of it are associated with more aggressive tumours, whereas the dry earwax variant could make some tumours more sensitive to chemotherapy. So eventually, earwax could help determine a person’s prognosis if they are diagnosed with cancer.
This article appeared in print under the headline “Ear witness”
