Smelly feet are due to bacterias which proliferate into a toxic environment.... So.... eliminatig toxins at times involves allowing these bacteria to proliferate.
Furthermore there are a few of these toxins which can ONLY be expelled through skin pores, with sweat. So all of these smell, depending on where your metabolism has stored the toxins will enivitably come out while cleansing.
This being said I never suffered from a smelly feet odor, yet I have had this armpit smell for quite a while, and this each and every time my metabolism would go into intense detox. I used to control it by forcing the sweat out in detox bath or at the sauna.
Ionic foot pad would seem a potent solution to your smelly problem!