Traditional whitening strips use hydrogen peroxide, which, when not administered by a dentist, can cause severe sensitivity, irritated gums, & damage to tooth enamel. Instead, our Whitening Strips are peroxide-free and use the clinically-proven active whitening ingredient PAP (Phthalimidoperoxycaproic Acid). PAP works similarly to peroxide, but it breaks down only the stains & discolouration and doesn't cause any sensitivity, irritation, or enamel damage.