For most teeth whitening products used in the home the active ingredient is bleach. The whitening gels used in mouthpieces or strips contain 10% carbamide peroxide, the teeth whitening bleach of choice. That’s equivalent to 3.6% hydrogen peroxide. Bleach at that level of concentration should not harm tooth enamel.
Home treatment may cause irritation in the gums and sensitivity in the teeth, however. The standard treatment for irritation in the mouth during the teeth whitening cycle is fluoride, which can be obtained on a prescription basis through your dentist.