Professional teeth whitening is a non-invasive cosmetic dental procedure with virtually no side effects. While the strength of the chemicals used in professional teeth whitening products can cause some temporary sensitivity or gum irritation, symptoms improve within 48 hours of treatment for most patients. Making temporary changes to your diet—such as limiting hot, cold, crunchy, or acidic foods—or using a sensitivity toothpaste can help minimize discomfort that persists beyond 48 hours.