The answer to this question lies in the type of bag that you are using, and the company that makes the bag. Designs that come on a roll typically are not used again because they are sealed on both sides and the users have to cut the plastic in order to retrieve their food. The zippered designed, on the other hand, can be used over and over again in most cases, you just need to ensure that you turn it inside out and wash it thoroughly with soap and water and let it completely dry before using it again.