My dog has allergies as well. We have taken him to the vet a couple of times and they perscribe an allergy pill that he can take 2 times a day. the only bad thing about this is it can be expensive! I have tried benedryl but he does not like it and it is very difficult to get him to take it. I would see your vet and look into maybe dog allergy med if you are planning on giving it daily.
There can be other causes of allegy-like symptoms besides a true allergy - particularly where eyes are concerned. Before trying to treat this yourself, have your dog evaluated by your vet first.