Children under age 3 should use under adult supervision. Do not submerge in water; the unit can be damaged. Change brush head every 3 months or sooner if the brush is worn or parts are loose. Failure to do so could lead to brush head breakage, generation of small parts and possible injury. After every use, remove brush head and rinse brush head thoroughly with water. Do not use brush with damaged or loose parts. Sensitive teeth and gums might be signs of an underlying condition. If you experience prolonged discomfort, stop product use and see your dentist.