The odour of feet is microbial work. The cheesy smell is caused by bacteria that break down the sweat of the feet, which would otherwise be completely odourless. Researchers found 80 species of microorganisms on the heel alone. The foot is a veritable land of milk and honey for bacteria: around 250,000 sweat glands produce a quarter of a litre of sweat.

 

The bacterial mixture produces three main odour-causing components: Methanethiol, which is notable for its foul odour, isovaleric acid with the characteristic cheese aroma reminiscent of rancid fat, and propionic acid with a sour note. The stinky foot is ready!

But which representative is responsible for the typical odour of sweaty feet? Foot odour and cheese have a surprising amount in common. In both cases, the intense odour and the characteristic aroma come from brevibacteria - small lactic acid bacteria. They live between the toes and produce the compound methanethiol (CH3-SH) when breaking down proteins in an oxygen-poor environment. Mosquitoes can detect this odour at a distance of 40 metres. In Africa, cheese is therefore even used to catch mosquitoes. Foot odour can even save lives!

 

However, the peaceful Brevibacteria are not solely responsible for the foot odour. Researchers see a connection between a noticeably cheesy foot odour and other microbes such as staphylococci or coryneform bacteria.

 

The only thing that helps against smelly feet is to make it as uncomfortable as possible for the bacteria. Freshly washed feet without calluses are less inviting, as are fresh socks and breathable shoes every day. However, it should not be forgotten that many important skin bacteria form the healthy skin barrier of the feet and protect against unwanted intruders.