One Click Smile uses hydrogen peroxide as the active whitening ingredient. Hydrogen peroxide is an ingredient found in many kinds of toothpaste and mouthwashes available in supermarkets. It is even used in very low concentrations to disinfect contact lenses. It can also be found in cosmetics and hair products. You can use hydrogen peroxide safely to whiten your teeth provided you follow the usage instructions included in your One Click Smile system and by discontinuing use if you experience an adverse reaction to the product.