Professional teeth whitening is a non-invasive cosmetic dental procedure that has virtually no side effects. The strength of the chemicals used in professional teeth whitening can cause some temporary sensitivity and gum irritation, but most symptoms improve within 48 hours of treatment. Discomfort that persists beyond 48 hours can often be alleviated by a temporary change to your diet, including limiting hot, cold, crunchy, or acidic foods, and by using a sensitivity toothpaste.