does not burn and smaells tastes good [SEP] this mouthwash does not burn even after flossing it lingers with protection for several hours although not hours that is refered to by colgate i have not had any black stains after weeks use i only use it one time a day thoughthis is an okay product just as good as any colgate i have used but i cannot say i notice a huge improvement over the regular total mouthwash