A lot of good points covered already from food and medication here. Unfortunately, it doesnāt sound like your vet knows the breed very well and it might be helpful to look for a vet that has a lot of experience with bulldogs. I especially want to mention this because even low dosage of steroids can make bulldogs susceptible to calcinosis cutis which is a skin issue that looks similarly like allergies. If you do a quick google search of calcinosis cutis bulldogs there are a ton of articles about this.