help student licking everything

Hi! I teach an autism self-contained class. About a month ago, one of my students started to lick his shoes. We ignored it, as this was a behavior in his past (about 2 years ago), and once it was ignored, it stopped. Ignoring didn't help at all. He started licking his shoes constantly, stopping in the hallway to lick his shoes, and now licking EVERYTHING - his iPad, the floor, thew walls, door knobs...seriously everything. We started doing "lick breaks" (a differential reinforcement schedule), and tried to redirect him to licking a lollipop, chewy, or spoon... I also have a social story. He now only has his corner of the classroom because my other students are constantly getting sick. I feel so bad, I can't think about any way to help him. Any ideas?