Foot odour is often more appreciated by the receiver than the giver.
The primary cause is bacteria living in a warm moist environment provided by sweaty feet.
One hundred and twenty five thousand sweat glands on each foot pump out a clear odorless sweat, these glands are called eccrine sweat glands and are found all over the body but are most concentated on the feet. They produce a thin watery secretion which cools us down by latent heat lost in evaporation. They differ from the apocrine sweat glands, located in the armpits and groin, which produce a much more concentrated sweat and are responsible for most body odor.
Because we mostly wear socks and shoes this sweat tends to accumulate, instead of evaporating harmlessly and creates a culture environment for certain bacteria that feed on dead skin and thrive in a moist warm environment .
Different bacteria are responsible for producing different odors; one bacterial cause of odour is Brevibacterium linens, digestion of dead skin produces a gas called methanethiol which smells of rotten eggs or cabbage. If your foot odour is more vinegary, it might come from Staphylococcus epidermis, this bacteria eats an amino acid found on the skin and produces isovaleric acid, commonly found in particularly pungent smelling cheeses. Large quantities of either or both of these agents can be seriously bad news!
Hygiene is important, wash your feet with an anti-bacterial soap and dry them thoroughly as bacteria like moist environments.
Wear cotton socks as these allow your feet to breath and help keep them dry. Change socks twice a day if necessary, washing them in a high temperature wash cycle. Take your shoes off as often as possible, again to let your feet breathe.
Clean the feet daily with isopropyl alcohol from the chemist for two weeks - this is considered a very effective cure.
It may help to sprinkle some bicarbonate of soda - ordinary cooking soda in your socks as this with create an alkaline environment which bacteria don't like.
Odour eaters and over the counter foot odour products may also help mask and treat.
Finally if the problem doesn't go away, see your doctor or visit a podiatrist- it could be related to a more serious problem