Carbamide peroxide (also known as urea peroxide) is the most popular at-home or over-the-counter bleaching agent used for teeth whitening. The main and active ingredient in carbamide peroxide is hydrogen peroxide. Carbamide peroxide has the effect of oxidizing stains, which leaves teeth looking whiter. Dentists usually use another product with carbamide peroxide or hydrogen peroxide when undergoing in-office teeth whitening, so when it's formulated into over-the-counter bleaching products, carbamide peroxide appears in a lower concentration.
