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.

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,........

© BBC