I could give a bullshit answer like I don't like rubbers...which is true. But it's deeper than that. I guess it's just breaking the rules. Probably deeper than that, but it's part of it.
I won't do a whore that's not GFE. Nothing deeper than I like kissing.
Do you have hygiene rituals for the girl?
When I was on the Angeles City kick I read a post from a monger who liked GFE but he took the girl longtime and made them use an iodine douche, Enema if anal was on the menu, shower under his supervision then 3 gargles/swishes of listerine and a finish with salt water. He was clear that he did not make them brush their teeth because that might make their gums bleed. He wouldn't wear a condom but if he was in the mood to eat pussy he used dental dams. He was quite verbose about his hygiene requirements.
I don't see how the iodine douche does anything.