Science Questions

Why do toenails smell like cheese?

Sat, 12th May 2012

Listen Now    Download as mp3 from the show Cracking Chronic Fatigue


David, Johannesburg asked:

Why do toenails smell like cheese?


We posed this question to Professor Kevin Kerr from Harrogate District Hospital...

Well, you could turn the question around the other way and ask why do cheeses smell like feet?  And if you did, you'll come up with the same answer.stilton blue cheese

And the answer is, bacteria - bacteria called Brevibacteria, which are used to ripen or mature certain types of cheeses can also be found growing harmlessly on the skin of humans especially areas where itís warm and moist such as sweaty feet.  

As the bacteria grow, they produce compounds which smell, well, cheesy and the chemicals responsible for this powerful pungent odour are sulphur containing compounds known as S-methyl thioesters.

If you've eaten asparagus, you may well find that your wee smells funny too and again, itís those S-methyl thioesters that you've got to thank, or blame, for your smelly wee.   

You may find something that actually looks like cheese underneath your toenails.  So, does this mean that our bacterial friend, Brevibacterium is actually making cheese under your nails?  Well, it may look like cheese, but it certainly wouldnít taste like cheese because what's going on here is that you've probably got a fungal infection in your nail, and the name for that is onychomycosis.  Onychomycosis can be tricky to treat, so itís best to see your family doctor to discuss the available treatment options.  

Hannah -  And onychomycosis toenail infections are caused by fungi known as dermatophytes and these dastardly dermatophytes produce an enzyme which acts on the nail.  Bad news for the nail, but good news for the fungus as the enzyme called keratinase breaks down the keratin in the nail to provide tasty treats for the dermatophytes.  

So, the cheesy appearance, that yellow and thickening nail represents the damage done to the nail by the fungus feasting on it.  But the cheesy aroma coming from the fetid feet is from Brevibacterium festering between sweaty unwashed toes and producing stinky S-methyl thioesters.   

And you are likely to get both the Brevibacterium cheesy pong in combination with the fungi eating hardened toenail as both seem to like warm, moist environments.


Subscribe Free

Related Content


Make a comment

Bacteria. Guthers, Mon, 30th Apr 2012

I don't think I have cheesy toenails.
But, if you have thickening and yellowing of the toenails, you may have a fungal or yeast infection. CliffordK, Tue, 1st May 2012

Like Guthers said, it's likely due to the bacteria.  The Brevibacteria that is used to ferment some cheeses is also present on our skin and concentrated around the feet causing odor.  Tray, Tue, 8th May 2012

Because milk and sweat are more similar than most people are happy thinking about. Bored chemist, Wed, 9th May 2012

& they taste like cheese 2!
CZARCAR, Wed, 9th May 2012

I think it's because of Propionibacterium but probably also cornebacteria and many others.

Basically, bacteria in cheese and those that live on feet will share some genetics, and thus will often produce similar smells. wolfekeeper, Sat, 12th May 2012

Did any of you even read the article above? Why are you all trying to answer the question (wrongly) that was answered already? Jay, Sat, 22nd Nov 2014

This is great, I clipped my toenails and sniffed them, smelled like Parmesan, and I started thinking up this imaginary world where Parmesan is a product scraped from beneath the toenails of giant trolls. Then I read this and was happy. Joshua K, Thu, 7th May 2015

Joshua your comment is wonderful. Darla, Sun, 17th May 2015

Ah this realization that cheese and keratin sceretions, when eaten by bacteria produce the same consistence and flavor/odor.... Did humans develop a like for cheese because it smelt like really masculine men(excess testosterone causes the secretions nessicary to feed the bacteria that create the smell). It certainly wouldn't even be close to the first time humans like something because it smells like a particularly virile/fertile man or woman Ohmy, Tue, 9th Jun 2015

My toe nail smells weird and it looks like it is gonna fall of I saw my doctor and she said it was fine but I disagree Joahua, Tue, 23rd Aug 2016

See the whole discussion | Make a comment

Not working please enable javascript
Genetics Society