A little hair of the bugs on the dog that bit you.
Bugs can and will set up shop en masse right inside your beloved pet's treat-hole. But these are no cute little ladybugs, they're actually a tough species of Asian lady beetles that can cause ulcers on the dog's mouth and tongue so severe they can be mistaken for freaking chemical burns. To be fair, the dogs bring it on themselves: The apparent cause is attempted canine nommage of the bugs, because there's no floor on the weird shit dogs will try to eat. Once they're inside that slobbery death trap, the beetles simply accept their fate and try to live the best life they possibly can inside your cute pet's trash-slide.
Thankfully, it's an uncommon and relatively easy-to-fix problem. If you notice your dog foaming at the mouth and refusing to eat, stop reading this comedy article and take them to the vet, Jesus Christ. But it wouldn't hurt to take a look down the ol' kibble tube first. If you happen to notice an entomological horror show, you can pluck those fuckers right off, provided your dog knows he's hosting a low-budget Pixar movie in his mouth and lets you. A spoon or tongue depressor can be used on more stubborn friends, but make fun of him for going down on a literal bush for a few days to teach him some humility.