According to what I just read the stuff works because of a blend of hydrosulfide salts. Hydrosulfide salts can easily convert to a pair of compounds, one of which being hydrogen sulfide e.g. bad egg smell.
(The other compund would depend on what type of hydrosulfide salt it started as, for example ammonium hydrosulfide breaks apart into ammonium and hydrogen sulfide. This is how a stinkbomb works in case anyone was interested.)