There are a few dog foods on the market that are similar to Purina HA. Royal Canin, Eukanuba, and Hills Science Diet all offer products that are formulated for dogs with allergies or sensitivities. These brands use hydrolyzed protein sources, which have been broken down into smaller pieces so that they are less likely to cause an allergic reaction. All three of these brands also offer prescription diets that your veterinarian can recommend if your dog has more severe food allergies.