Your child should be at least 12 years old before you start introducing them to products such as mouthwash and whitening products. At this point, they’ll have all of their permanent teeth. Consult your family dentist if you want to try a whitening treatment. OTC whitening strips or rinse or toothpaste may be more viable options to try before pricey professional whitening procedures that insurance does not cover. And because stained teeth can be caused by a diet that needs a nutritional boost, try to pinpoint the cause with your dentist before embarking on a treatment.