In New 杏吧原创鈥榮 recently published book Does Anything Eat Wasps? there was a question about athlete鈥檚 foot. I used to suffer this to excess until my father told me to pee on my feet when I shower. I鈥檝e never had it since. How does this 鈥渃ure鈥� work?
鈥� Athlete鈥檚 foot (or tinea pedis) is a skin infection caused by several different ringworm fungi: the most common culprits are Trichophyton, Microsporum and Epidermophyton. Ringworm fungi grow best at 35 掳C, so when skin stays moist and warm, ringworm thrive and infect toenails and upper layers of the skin, digesting the keratin there. Ringworm fungi can be picked up from floors or clothing, and can live anywhere on your skin, but without suitable conditions 鈥� the warm, moist environment of a sweaty socked foot is ideal 鈥� they will not cause a noticeable infection.
Most treatments involve keeping the skin drier or applying fungicide, and at first glance urine appears to have antifungal effects. While mostly water, it does have organic products such as urea, uric acid and creatinine, some of which are antifungal or antibacterial. Urea paste is used to treat nail fungal infections, because it denatures proteins in the epidermis.
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However, peeing in the shower is probably not providing the cure, because urine only contains around 18 per cent urea 鈥� the pastes have to be at least 40 per cent to work 鈥� and must be left on the skin for several days. The urea in the paste softens the skin and allows antimycotic medicine that kills the fungus to penetrate. The urea in your urine is not concentrated enough, and if you are peeing in the shower, it is being washed off too quickly to have any effect.
So the most likely answer is that knowing that you have peed on your feet you will rinse and/or dry them especially carefully (maybe even subconsciously), which removes the dead skin cells the fungi use as food.
Jo Burgess, Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, Grahamstown, South Africa