Pet food allergies are often protein related which is one reason why most Halo diets are formulated with a single species protein such as turkey and turkey liver, chicken and chicken liver, or fish combinations, so if your dog has a chicken allergy, for example, you can choose one of the other protein formulas. Also, all Halo diets are formulated to be free of animals raised with antibiotics, artificial colors, flavors or preservatives. Whole grain and grain free recipes are also available.