Actually allergies to things in the environment happen much more often that true food allergies in dogs. Of course, if your dog was clear just a little while ago and only now has symptoms you may get lucky in ID'ing the culprit. But sometimes the dog is allergic to something that is seasonal (like people's hay fever) so it's possible that the change he is reacting to is actually some pollen or mold or whatever (though it is winter, so that might be unlikely.)
If you do decide to run a limited diet trial, you need to find a food that he has no symptoms with and then add protein sources one by one with a month or more between new foods.
I thought ..... hoped it was seasonal. But w/ all the ice we have it got worse!
Sooo I’m going to eliminate the possibility of “seasonal” I do the food trial.
I of course gave him more treats because of him being indoors & bored. We are in Dallas, That’s why I posted on here, because it did in fact get worse.
This morning his eyes were twice as bad as they have been.
sooo yeah - I’m thinking it’s food allergies.
not 100% but my gut tells me it’s the crap I’ve been giving him. 🙄😕