What's The Science Behind Smelly Feet?
With the weather heating up, I have noticed an old foe resurfacing… my smelly feet. Though this isn’t a huge problem for me (Thank you, Peditech!), I thought it would be interesting to see what actually causes my cheesy issues, and the issues of more than 80% of the UK population (Newbury, 2018).
As you can probably guess, one of the major culprits involved is sweat. Human feet have 250,000 sweat glands and can produce more than one-third of a pint of sweat a day. This sweat is trapped by our socks and shoes which creates a long-lasting warm damp environment filled with salts, sugars, and other minerals – the constituents of sweat (Patterson et.al., 2000). It isn’t, however, the sweat itself that causes the smell, but bacterial colonies feeding on the sweat and excreting out the odorous compounds (Barzantny et.al., 2012). This is the case for most, body odours.
There are several bacteria that have been found to cause foot odour, with the largest culprits being Staphylococcus epidermidis, Bacillus subtilis and Corynebacteria species (Ara et.al., 2006; Taylor et.al., 2003). The compound being produced, with such a recognisable scent, is Isovaleric acid. This acid is what gives feet their stink, cheeses their waft and even the hoppiness of beer. It has been determined that the microbial communities on our skin determine the exact scent of our “sweat”, moreover, several mosquito species determine who to bite due to these bacterial excretions (Verhulst et.al., 2011). This discovery that mosquitos are attracted to specific compounds on our skin, which I personally had suspected due to being the one that is always bitten, has also helped in research surrounding malaria transmission. By understanding what is attracting malaria-transmitting mosquitos, we may be able to take steps towards reducing transmission and therefore lessening the impact of the illness globally.
I did, sadly, notice that many of these studies had a heavy masculine volunteer presence. If you have ever smelt the difference between a men’s changing room and a women’s, you will understand why I believe it to be important that studies on scent origins should be more diverse. In one case there were 52 men and only five women.
As for how to help with smelly feet… keep them as clean and dry as possible, try products like Peditech (I’m not on commission, it’s just been a lifesaver for me and my partner!) and antibacterial soaps. Importantly, remember that it is not you, it’s those pesky bacteria.
References:
Newbury, A. (2018). New survey highlights nationwide problems with smelly feet. Available: https://www.mediplacements.com/article-801847440-new_survey_highlights.html. Last accessed 22/06/2021.
Patterson, M.J., Galloway, S.D. and Nimmo, M.A., 2000. Variations in regional sweat composition in normal human males. Experimental physiology, 85(6), pp.869-875.
Barzantny, H., Brune, I. and Tauch, A., 2012. Molecular basis of human body odour formation: insights deduced from corynebacterial genome sequences. International journal of cosmetic science, 34(1), pp.2-11.
Ara, K., Hama, M., Akiba, S., Koike, K., Okisaka, K., Hagura, T., Kamiya, T. and Tomita, F., 2006. Foot odor due to microbial metabolism and its control. Canadian journal of microbiology , 52 (4), pp. 357-364.
Taylor, D., Daulby, A., Grimshaw, S., James, G., Mercer, J. and Vaziri, S., 2003. Characterization of the microflora of the human axilla. International journal of cosmetic science, 25(3), pp.137-145.
Verhulst, N.O., Qiu, Y.T., Beijleveld, H., Maliepaard, C., Knights, D., Schulz, S., Berg-Lyons, D., Lauber, C.L., Verduijn, W., Haasnoot, G.W. and Mumm, R., 2011. Composition of human skin microbiota affects attractiveness to malaria mosquitoes. PloS one, 6(12), p.e28991.
Written by Libby Bowles
I’m a PhD Researcher at Prifysgol Aberystwyth, studying the perenniality syndrome in Grasses. I’m passionate about public engagement in science and the sharing of knowledge regarding the world we live in, especially the weird and wonderful.