Have to agree with Flirt Attendant there, you need to update your shoes regularly in this job.
Aside from clean feet, fresh hosiery every day and medicated foot talc, peppermint foot lotions (Body Shop etc) are also good for smelly and tired feet. Without sounding too gross fungus buildup is what usually causes smelly feet and some feet grow this faster than others making them extra smelly. Like my sisters
( sorry Sis but you know it's true ).
Anyway hope your friend sorts it out poor thing, things that pong are not nice in the cabin for anybody.
