Ummm! Actually they do according to the manufacturing companies. I have been in contact with Zip-Loc and Glad companies and they both say that in no way were their bags made or designed for any type of cooking. To do so could be dangerous as they do release toxins into whats boiling that you put in them. Minute amounts but over the long haul it couldn't be a great idea. That's from the horses mouth...sabre11004...