Brushing activates them, causing them to produce a blue foam that has a temporary effect. Brush your teeth for 2 minutes, 3 times per day. Children aged 6 and under should only use a pea-sized amount and should be supervised by an adult to avoid swallowing. Consult a dentist or doctor if you have consumed fluoride from other sources. Avoid swallowing. After brushing, thoroughly spit and rinse. Clinically Proven Optic Brighteners Are Included in the Formula.