YI after oral sex?

[lightningxsnow.livejournal.com]

I find that after someone goes down on me without a dental dam, especially if it's a new partner, I tend to feel like I get a mild yeast infection - I get itchy and sometimes there's a change in smell.

Is this a YI or something else? And is there any way, besides using a dam, to prevent it? (I don't have much of a problem using dams with casual partners, but I'd rather not use them with my girlfriend. Personal preference.)