My 11-mo. GSD and I love to take daily walks/runs in the woods, but right now the deer flies are horrendous. I wear a veil and shirt. but even though he has a very thick coat, the poor dog's ears and head are often dotted with flies. Would it be harmful to spray the back of his head and ears with Off? I have tried it a couple of times and it works very well but I don't want to harm him.