Chewables may be a choking hazard and are not recommended for children under 18 months. Use the following tips to keep your child safe and avoid overdosing: Give every six to eight hours as needed. Don't exceed four doses in 24 hours. The body absorbs ibuprofen quickly, especially when it's taken as a liquid or chewable tablet. This means that children's ibuprofen will start to work about 15 to 30 minutes after the medicine is taken.