IF I was looking at a human I would suspect flesh eating bacteria. MERSA or when my son was a little he got strep and that turned to scarlet fever then all the skin on his feet sloffed off. Can you take this chick to a vet and possibly culture that mess ? I wouldnt have a clue if chickens could get any of these things but it looks serious enough that I wouldnt even want to touch it with my bare hands. It could be something as simple as an allergy but it could also be a staff infection. Contagious to humans .