That said, there are still risks associated with these products, like increased sensitivity and gingival irritation (inflammation). These are increasingly likely when whitening is done outside of registered medical settings. Hydrogen peroxide- and carbamide peroxide-based tooth whitening is safe and effective
(when you follow the manufacturer’s instructions or it’s done by a professional) but there is a risk that acid-based whiteners can thin your enamel, says Dr Patel. "More of the underlying tooth structure will shine through as time goes on. You might see a short-term uplift in colour but if you continue long term, you may have your teeth get dramatically more yellow, which can be difficult to fix." Equally, high-concentration solutions of bleach would be very effective if used in a controlled environment, says Dr Patel, who adds that they could be extremely painful if not used correctly with well-fitting whitening trays.