my dog has a few bare patches of hair on his face. What could be causing this?

On my dogs face and neck there are 3 small bare patches where there is hair missing. Two of the places can be explained (he scratches his lower jaw and neck a lot.) The other place (right below his left eye) can't be explained that I know of. He is not around other dogs. What can cause him to have bare patches of hair like this?

I'd have him checked for mange. Dogs have mange mites and sometimes their immune systems aren't strong enough to fight them off and they grow.

He is making bald spots by rubbing and scratching. Have the vet check him for mites. He might also have a food allergy.

The missing fur around the eyes could be mange, or any number of things. Your vet can do a painless skin scrapping of the area and tell you what is going on in a matter of minutes. As I volunteer in a shelter, I see some mange, and thinning fur around the eyes is an indicator of it, but its impossible to know until the vet determines what is going on with your dog. Good luck. And btw, there could be numerous reason for the missing fur besides mange, mites or allergies. So don't worry, but be cautious and consider having your vet check it out.