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03 November 2020

Earwax sampling could measure stress hormone

New research co-led by King’s College London academics suggests a novel method to sample earwax could be a cheap and effective way to measure the hormone cortisol.

Woman resting chin on her hand looking off to the side

Cortisol, known as the so-called ‘stress hormone’, has been considered as a possible biomarker, or objective biological measure, for depression. However, researchers have been stymied by challenges in accurately measuring cortisol levels. The most common measuring technique uses hair samples, but they are more subject to short-term fluctuations in cortisol level, and not everyone has enough hair for a reliable sample.

Analysing earwax has been considered as a quicker and cheaper way to test cortisol methods compared to hair, but until now there has not been a reliable and non-stressful method to sample earwax.

Now, researchers at King’s and UCL have developed a new device that allows effective earwax sampling. The new findings, which have been published in the academic journal Heliyon, could point to new ways of monitoring depression and stress-linked conditions.

The new device can be used at home without clinical supervision, facilitating medical check-ups while maintaining social distancing due to COVID-19, and may also have the potential to measure glucose or COVID-19 antibodies that accumulate in earwax.

Cortisol sampling is notoriously difficult, as levels of the hormone can fluctuate, so a sample might not be an accurate reflection of a person’s chronic cortisol levels. Moreover, sampling methods themselves can induce stress and influence the results.

Lead researcher Dr Andres Herane-Vives, from the Institute of Psychiatry, Psychology & Neuroscience at King’s and UCL Institute of Cognitive Neuroscience

He added ‘But cortisol levels in earwax appear to be more stable, and with our new device, it’s easy to take a sample and get it tested quickly, cheaply and effectively.’

To develop the new device, Dr Herane-Vives was inspired by another natural wax, honeycomb from bees, as it is known to be well-preserved and resistant to bacterial contamination. Earwax has similar properties, making it well suited for home sampling, as samples can be sent to a lab by post without much risk of contamination.

The novel earwax self-sampling device is similar to a cotton swab, but with a brake that stops the swab from going too far into the ear and causing damage. The tip is covered with a sponge of organic material, with a solution that has been tested to be the most effective and reliable at taking samples.

In their pilot study, Dr Herane-Vives and a team of researchers from the UK, Chile and Germany brought in 37 study participants to test different cortisol sampling techniques. The research team sampled participants’ earwax using a standard syringe procedure, known to be somewhat painful, and then followed up a month later by using the same sampling in one ear, and the novel sampling technique in the other ear, which the participants could administer themselves. The researchers also analysed hair and blood samples from the same participants.

The researchers found that earwax samples yielded more cortisol than hair samples, and the new technique was the fastest and potentially cheapest method. The novel technique was the least influenced by confounding factors such as stressful events or alcohol consumption contributing to cortisol fluctuations over the previous month. In another recent study, participants rated the new self-sampling device as more comfortable than traditional methods.

He and his team are also investigating whether the device could be useful to measure glucose levels from earwax samples, for monitoring of diabetes, and potentially even COVID-19 antibodies.

After this successful pilot study, if our device holds up to further scrutiny in larger trials, we hope to transform diagnostics and care for millions of people with depression or cortisol-related conditions such as Addison's disease and Cushing syndrome, and potentially numerous other conditions.

Lead researcher Dr Andres Herane-Vives, from the Institute of Psychiatry, Psychology & Neuroscience at King’s and UCL Institute of Cognitive Neuroscience

Dr Herane-Vives is now setting up a company, Trears, to bring his earwax sampling device to market, with support from the UCL Hatchery start up incubator.

The paper is available here.


For further information please contact: Alice Kay, IoPPN Interim Senior Press Officer, / +44 7718697176