Whales never clean out their ears. Year after year their earwax builds up, leaving behind something of a life history told in fatty acids, alcohols, and cholesterols. The waxy substance builds in the ear canals of many mammals, including ourselves. Human earwax, on the other hand, is not nearly as interesting. It doesn’t offer up an autobiography, and most of us remove the waxy build-up from our ears fairly regularly (about which, more later). Still, there’s a fascinating science underlying the humdrum substance.

The proper name for the stuff is cerumen, and it’s produced only by the outermost bit of the ear canal, thanks to a mix of between one and two thousand sebaceous glands (which, on your head, also help to keep hair oily) and modified sweat glands. Add some bits of hair, dead skin, and other bodily detritus and you’ve got the recipe for earwax.

Its main function has long been thought to be primarily one of lubrication (which is why early lip balms were made of the stuff) though it’s also believed to be useful for preventing insects from creeping their way into the internal recesses of your head. But some suspect that earwax also functions as an antibiotic.

In 1980, NIH researchers Tuu-Jyi Chai and Toby C Chai collected cerumen with a device they refer to as a “sterile earwax hook” from 12 people, and mixed it all together in an alcohol solution. Then they introduced some bacteria to the party. The earwax managed to kill off 99% of several bacteria strains, including H. influenzae (which, confusingly, doesn’t lead to influenza, but a different type of infection) and a particular strain of E. coli called K-12. Other strains of E. coli, andStreptococcus and Staphylococcus, were a bit more resistant to earwax, with mortality rates varying between 30% and 80%. Still, the collected earwax had clear bactericidal effects on all 10 types of bacteria they tested.

Similar results were found in a 2011 German study. In that experiment, 10 peptides found in earwax were able to prevent bacteria and fungi from growing. External ear canal infections, the researchers argued, are what results when the earwax-based defence system fails.

Whether you have wet or dry earwax is genetically determined

But in 2000, a study conducted at La Laguna University in the Canary Islands found the opposite. Instead, researchers found a neutral effect when it came to one strain of Staph, and in most cases, they found that earwax actually promoted the growth of bacteria, including E. coli, ostensibly due to the rich nutrient bounty it provides. It’s not the only study to cast doubt on earwax’s propensity for microbial murder.

There’s one thing that might shed light on the wildly differing conclusions that these and other studies have put forth. The 1980 and 2011 studies used wax from people with dry earwax, while the 2000 study focused on the wet form. It’s by no means clear that this distinction underlies earwax’s putative antimicrobial properties, but it’s a beguiling hypothesis, especially since the two types are essentially made from the same ingredients. Still, unless you’ve surreptitiously taken a peek into your friends’ ear canals, then you might be surprised, as I was, to learn that there are two different kinds. In the name of full disclosure, mine is wet.

Read more