Oregano and various herbs that are commonly used for spicing Italian foods are wonderful properties of being pain antimicrobial. They help kill fungus and bacteria in various foods and plants. If you have tomatoes just a little bit beyond what they should be then making a tomato sauce with them can help destroy any organisms in them and any fungus. The cautions although is that you can still have an allergic reactivity to the fungus that has been killed in those sauce and the second question is these important herbs have essential oils and those essential oils although they can be beneficial to killing viruses in bacteria and fungus in your body, can also cause hypersensitivity reaction. Some people do get allergic to these oils and those people need to avoid them. Oregano is a very valuable herb as well is related herbs, but you need to know not to use it if you have a hypersensitivity and not to depend upon it to destroy the presence of allergens that were previously infectious in your foods.