The professional PAP+ gel in the Luxury Whitening Pen is peroxide free. Peroxide is a bleaching agent that is harmful to teeth. Our formula is composed of natural ingredients that give the same result as peroxide containing methods. Only with the peroxide-free gel will your enamel and gums not be affected. Peroxide affects all tooth molecules and our gel only focuses on the discolored molecules. This together makes for the other result. With one Luxury Whitening Pen you can do 15 to 20 sessions. This is more than enough to achieve and maintain the desired white shade. The ingredients list describes exactly what each ingredient does.