I think there was a blooper thread here where a chick couldn't, for the life of her, bring herself to go down on a guy in a glory hole because of the smell. And she ended up puking. I only saw the beginning when she started to gag. Had no interest in watching the rest of that disaster. Haha.
Seriously, though... If a chick is kind enough to suck you off, the least you can do is to practice decent hygiene.