 [ Symptoms ] i have rinsed my mouth with peroxide every day for a while could this cause white spots inside my mouth and on my gums [ Disease ] pure peroxide is a very caustic substance that can burn tissue if you want to rinse with hydrogen peroxide you must dilute it with water at least a 21 ratio of water to peroxide peroxide does help kill a lot of germs but use it in combination with mouthwash and regular flossing