Smelly feet
Nature
Foot odor (also spelled foot odour) or bromodosis is a type of body odor that affects the feet of humans. It is sometimes considered to be an unpleasant smell, but can also be the target of foot fetishism, more specifically as a form of olfactophilia.
It is one of the most widespread forms of olfactophilia: In a 1994 study, 45% of those with a foot fetish were found to be aroused by smelly socks and/or feet, but most importantly by the intensity of the smell produced by such bacteria. Foot odor is often caused by foot sweat and the accumulation of bacteria, which creates an odor. The odor can exhibit varying qualities depending on the state of the feet.
Source: Wikipedia
Broader
Aggravated by
Type
(G) Very specific problems