After determining your dog has food allergies, you will want to change their diet to a hypoallergenic food; this means more than just swapping brands. Your vet will often recommend different options, including protein and carbohydrate choices, as well as brands that specialize in this.
You must read the full ingredient list; if a label states turkey and rice, it does not mean that it will not contain other ingredients such as beef, chicken, wheat, etc.
Additionally, your vet may also suggest putting them on a prescription diet. Prescription diets are formulated to reduce the allergen levels in the food to the point that your dog will not react yet still receive the proper nutrition.
The benefit of a prescription diet is it has grains and proteins that your dog needs to maintain a healthy lifestyle. However, prescription diets can be costly.
In more severe food allergy issues, they may recommend prescription medications such as
Cyclosporine, Apoquel, or Cytopoint.