what is this skin allergy my dog keeps getting?

My dog is a 3 year old rottweiler and the past few month he keeps getting agraveted by something he licks and bites where it is causing his fur to fall off when I have looked at at the skin is flaky n dry and starts to puss ang have a foul odour has anyone eperinced anything like thisI have been to the vet and it keeps coming back they give me this diluted ontment to dab on bt I think it needs clearing up from the inside

Whatever it was, he now probably has a bacterial infection. Take him to the vet to start figuring out what caused it and to get antibiotics to clear up the infection.