Hi,
I don't have a boston yet but I have a bullmastiff who has terrible seasonal allergies. She gets cortisone shots to help relieve her symptoms. When she has the allergies it's awful, she chews herself til she bleeds, her eyes get all weepy and her face breaks out. We've tried everything and benadryl for us doesn't help. The cortisone shots only last about 6 weeks. This past time she had to have a higher dose. We've tried oral prednisone and unfortunately these steroids are not permanent long term solutions. It can have a serious effect on their other organs. We have tried holistic treatments too. I don't know what to tell you other then maybe bring your dog to a vet who specializes in dermatology. We haven't spent the money on allergy testing yet as we heard it's expensive and there's no guarantee. We may go that route depending on how she does.
Good luck.
I sympathize.
Rachel