If your child somehow manages to swallow some shampoo — which can happen during bathtime as babies love to chew on their washcloths — Poison Control says it's unlikely to cause harm. If they swallow a significant amount, they may experience vomiting or diarrhea. If your child swallows what you think is a large amount of shampoo, or is having persistent gastrointestinal symptoms, call Poison Control (1-800-222-1222) or your pediatrician immediately for further guidance.