English Bulldog

So I have a 2 yr old English bulldog (pic below) and she’s been scratching a lot. A month or so ago she had an allergic reaction to something and broke out in hives (about the third time it happens but not frequently) I am afraid it’s going to happen again because she keeps itching. Like she’ll spin on her bottom trying to scratch herself (it’s not worms) or is just up all night scratching her belly (since it’s the only part she can reach) and when we take her to the vet there’s only so much they can do. Since we don’t know what’s causing this it they would have to do a test to see what she’s allergic too but it’s $600 and we just don’t have that kind or money right now. I know this breed is prone to all sorts of allergies specially skin allergies. We’ve given her multiple dog foods from Royal Canin, Purina, blue buffalo wildernesses, some heritage (I think it’s an H-E-B brand) right now she’s on whole earth farms. We think she was allergic to chicken (RC brand had chicken but we had been giving her that since she was a puppy so I’m not sure why all of the sudden she got that allergic reaction. So now we only give her dog food with salmon, grain free, no potatoes.) I just don’t know what could be wrong with her and I feel like taking her to the vet wouldn’t help if all they will do is offer that test.. this is Peaches.