Afraid of Flies

My 62 lb. male Airedale is afraid of flies. Yes, it is quirky and we find it part of his particular or should I say peculiar charm but we would like to have him outside more in the summer. Does anyone know of a safe way to keep the flies off? If we get one in the house he runs down the hallway and peeks out at us until we kill it! :shrug:

At the pet store the other day I happened to see citronella type sprays for dogs. Don't know if they keep flies away though.

He probably was stung by a wasp or a bee and so associates the buzz of a fly. Not much other than sprays and fly traps to help.