The only thing that ever worked for my dog was vaseline petroleum jelly. I would put it on the tips of his ears and it sticks so it lasts longer, kept the flies from biting his ears.
I also used the deep woods off wipes around his neck and chest area. Only put it on areas the dog cannot lick. It helped keep the flies away.
If you have a high area near where the dog lays put up a fly tape. They are sticky so put it where you won't run into it and the flies are attacted to the tape and get stuck.
Hope this helps you. I will ask my friends about this problem as well, and keep you posted.
