what’s wrong with my dog?

She keeps letting these all over her feet gets bumps on her body, loses hair in areas, the vet have no clue what’s wrong , they ran tests she has no infections or bugs , treated her for ticks and fleas just to be extra sure , treated her for mange she just in case a big chunk of money later no answers it been months I don’t want her in pain . But it’s still here , I’m starting to think allergies because when she was a little pup 11-12 weeks she would get these bumps but in smaller amounts just figured it was part of being a pup never seemed serious thought it was “bully bumps” she has been on the same food this whole time . Anyone ever seen this?