Help Getting Rid of Biting Flies

In the first place, flies don't normally hang around dogs.

The flies, however, do hang around areas of the skin which have been broken. They will lay their eggs in the wounds. That makes that part of the skin itchy. The dog scratches it and more skin is broken. Which attracts even more flies.

So I would say, the first thing to do, is to treat the skin. Clean it with antibiotics and apply acriflavin on it. Iodine, if the condition warrants it but, remember, iodine is very biting. Then find a way to keep the dog from scratching the afffected part. A cone should work, in most cases. Of course, the dog should be bathed more times than usual to keep it clean and, more importantly, smelling clean.

It's the smell of the rotting flesh in the wound which attracts the flies.