How Do I Stop My Dogs From Constantly Scratching Their Skin Raw?

Do they have fleas fist of all?
They may be allergic to the Advantage .
This is fall  they may be allergic to the grass or harvest, or if you are using carpet fresh  of any kind they can have a reaction to this on your carpet.
Depending on size you can give them benadryl they have the children beadryl doses to you must check with a vet to know what dose to give them or you could make them sick or they could die if you over dose them this is important the correct dose.
I give it to my dogs as needle in a treat I fold the melt away ones up and they eat it .
This benadryl would help for th itching in both cases the fleas itch or allergy.
Next have you had a skin scraping done at the vet or have they seen a vet if not they should  this sounds very serious.

The skin scraping can tell you what it is they could have Mange or and a skin infection .

This could kill your dog if it is this bad please have the vet check for mange .
The ver can give them a antihistamine shot and a lotion there is also sprays he can prescribe to help them .
Please call and talk to your vet

Adding some alovera juice and apple cider vineagar to their diet can help to

You can put a cone on your dog.