My dog is always biting his fur

Try getting some FOOD GRADE DE powder. You can probably get it from a health food store or (I know) you can order from Amazon. Anyway, when you get it, put some in a sock & rub/pat all over your dog, especially where he’s biting. This will take care of mites & fleas and will work very quickly.
Good luck! Let me know how it goes.

it could be hot spots, not sure what exactly they are, but just kinda random spots that itch and dogs chew at until they make themselves raw and in more sever cases, bleed. I’d guess it’s something fungal or bacterial, maybe, but just guessing. I live in Florida so there’s alot of both here. One of my dogs has them regularly, with a really bad episode just recently. I mixed up a concoction of witch hazel extract with iodine and tea tree oil and she was better within a day or two. Mostly witch hazel with equal parts of the other two. I got everything at walmart, including the spray bottle i put it in. I’d spray it directly on her MANY spots, then rub it in. She didn’t like it much at first, but the tea tree oil is a topical analgesic, so it was soothing after the first minute or so. I did have to make her wear the cone of shame the first day, to keep her from chewing in between treatments, but after that she healed pretty quickly.