Since most of my problem foods are among the 8 most common allergens, many times a quick scan for the major allergens is enough to reject a food product. For example, any mention of milk, tree nuts, or shrimp, and it’s out. But if it mentions wheat (gluten) or soy, I look further.
If the soy is in the form of soy lecithin or soybean oil, I can have it. Protein content in lecithin and commercial oils are so low that most people with allergies will tolerate these.
If the only source of wheat and soy is soy sauce, I can usually have it. Gluten content in commercial soy sauce is under 20 ppm for most brands and I can tolerate small amounts.
Of course this all depends on one’s sensitivity level, but knowing these exceptions can open up quite a few more options.