Sugar, saliva, blood
The mouth is such a mighty machine, equipped with teeth and a tongue to pulverize food matter and a buffet of bacteria that chemically break it down further. The very tools that enable the mouth to do it's job well disgust me; a writhing tongue, harmful bacterial, stinking saliva. When exactly the mouth became viewed as a sexual organ I do not know, however, at times the notion that it can be a source of arousal is unfathomable to me.
Saliva, phlegm, gelatin