No one's eager to coat their throat in man gravy, but when a woman has just performed a, erm, service for you, refusal of any forthcoming affection can be insulting. So if you see a kiss headed your way, suck it up. Contorting your face in disgust will only make a woman feel cheap. If you can't stomach the thought of a post-fellatio tongue dance, kiss her neck, shoulders, face, etc. until such time has passed that any offending you-goo has dissolved.