mouth fetish
One who gets sexually aroused by anything and everything mouth related have a mouth fetish. It is manifested by an obsession with stimulating the mouth. These may include sucking, licking or simply just getting sexual pleasure from staring at an open mouth. Also see: Freud's theory on oral stage.
Marie has a mouth fetish. She first realized this by looking back at her photo collection of actresses sucking on their fingers, which she had collected without even realizing said perversion. Her friend explained to her that she must have developed said fetish because she was never breast fed as a baby. Now Marie gets the most intense pleasure from everything related to the stimulation of the mouth, both others' and her own. The story has a very happy ending: Marie has now come out of the closet as a raging mouth fetishist.