Many dogs suffer from food allergies.  They may need to avoid certain proteins, grains, or vegetables.  I have two dogs with food allergies and it became more and more difficult to find treats that they could enjoy.  I finally began to make my own.  These can be adjusted by using whatever grain or protein source your dogs can tolerate.   Just work in until the consistancy is manageable.   If cooked slowly they become just as crisp as the store bought variety.  Dogs love them.