whitening strips can whiten teeth Teeth whitening strips have the potential to whiten your teeth by bleaching stains with hydrogen peroxide or carbamide peroxide. Carbamide peroxide is a molecule that breaks down into hydrogen peroxide when it comes into contact with water. Peroxides in whitening strips penetrate the outer layer of your tooth called the enamel and enter the deeper dentin layer, where they bleach chromogens. Chromogens are pigmented molecules found inside and outside your tooth that cause staining. Staining can be divided into two categories: extrinsic and intrinsic staining. Extrinsic staining Extrinsic staining affects the outside of your tooth and is largely caused by environmental factors such as: smoking certain foods and drinks such as coffee, wine, dark berries antibiotics exposure to metals such as iron or copper Intrinsic staining Intrinsic staining affects the inside of your tooth. It’s caused by factors such as: age-related enamel erosion genetics antibiotics exposure to high levels of fluoride tooth development disorders Whitening strips target both extrinsic and intrinsic stains Whitening strips can target both types of stains. Stains caused by aging, genetics, smoking, or coffee are generally the fastest to respond to bleachingTrusted Source. Yellowish aging stains also respond well. Whitening strips may be best used when you’re trying to make a small touch-up to your tooth color. For more significant changes, you may want to consider professional whitening from a dentist. A dentist can use stronger bleaches and give you a custom treatment best suited to your needs. When it comes to effectiveness, ingredients matter Home whitening strips generally contain hydrogen peroxide or carbamide peroxide to bleach stains in your teeth. However, some strips, especially those used at some beauty salons or cruise shipsTrusted Source, may contain chlorine dioxide. Chlorine dioxide is touted to be a safer and more effective alternative, but its safety is debated. Chlorine dioxide may strip your tooth enamel. It may also make your teeth more prone to restaining and becoming extremely sensitive. Here are some of the whitening strips we recommend that use hydrogen peroxide as their active ingredient. (You can purchase online by clicking the links.)