How Much Is That Kitty in the Window

My beautiful black, long-haired cat has developed red sores on his face. First, one in front of his left ear, then, another in front of the other ear. Before my husband could take him to the vet, another spot appeared just above one of his eyes. We couldn't figure out what could be causing such sores. The vet asked if the cat goes outside. No. Does he sit in an open window? Yes, every morning my wife opens the window for him to hear all the sounds and sniff all the smells. The vet promptly diagnosed an allergy to ragweed. Yes, an allergy. Now who would figure that our household where every member has an allergy or two would also have a cat with allergies? The vet gave him a shot of cortizone, and the sores are healing quickly. I wonder if the cat that I am allergic to could be allergic to me? That would be poetic justice.