Lilly Blue

Hi all, was wondering if anyone has some advise please. Our beautiful staffy is loosing hair on her back, head and tail... the vet isn’t sure what it is, bloods and skin scrape show nothing other than a healthy 4yr old girl. I am worried it will get worse and it’s already looking very bad. I can see/ feel raised bumps In the patchy skin areas. Has anyone had anything similar with their staffy? Thank you