Homemade dog food is safe, natural, and if your dog is allergic to something, then you can voluntarily exclude that from their meal. You will also be able to keep a check on the nutritional value and also the calorie level, which is sometimes not possible in the case of food purchased from shops.
If you are going for commercial dog food, then you should always go for the best dog food brands. You should go for something that contains chicken or lamb as the most important ingredient. If the food just mentions 'Meat', then it's best that you avoid that. Some branded dog food also contains corn and bran. These are not suitable for dogs with allergies, as the corn present in the food can cause itching, licking of the paws, or sometimes ear infections. Hence, it's best to avoid dog food which contains corn. There are also some dog foods for allergic dogs which you can try. Just make sure that all the important ingredients are present in the food and that your dog is not allergic to any of them.