My dog is losing little patches of fur on her body any suggestions?

ok i have a miniature pitbull, her name is Roxy, well i noticed shes been losing little patches of fur and where it is it looks like bites, now heres the weird thing I took her to the vet and she doesnt have fleas or ticks, they wouldnt perscribe her anything, so i was knda pissed, but i told the vet that she stays in thehouse when im home but when im not shes outside. im thinking maybe there are flies biteing her, they said that could be it, but what my question is that IS THERE ANYTHING I CAN GIVE HER OR DO FOR HER TO HELP HER FUR GROW BACK.?