hello there, Thank you for posting your query with healthcare magic, first of all, I would like you to see a pediatric/general dentist who can show you the amount of tooth paste we should use for kids under 3 years of age as they cannot spit into the sink while tooth brushing. Tooth pastes contain fluoride in them which can cause upset stomach if swallowed in large amounts, also it may affect the tooth formation in babies, rarely though but we just have to make sure we are not overdosing them with fluoride. A size of a grain rice is the amount of toothpaste which we as dentist recommend on the toothbrush for babies teeth . If you have any further questions, feel free to post them here. I hope I answered your query, thank you