It does seem like you have given it some time for his skin to heal, but I know that once they get an allergic reaction and it affects their skin, depending on how bad it got, it can take time to heal. With that being said, if it doesn’t heal you may have to put him on apoquel, which you will have to get from the vet. That helps tremendously with skin conditions and allergies. Maybe try sprinkling something on his food. Like, some freeze-dried raw food (primal, Stella & Chewy) or Etta Says Liver Sprinkles, this will entice him to eat his food. The liver sprinkles are a miracle. I would still have his thyroid checked and his blood sugar level for the excessive drinking. I hope I was a little bit of help. Update when he gets back to his old self. Best of luck.
