When will the product start to work? Every child is different, but generally, fever and/or pain is reduced within about 1-2 hours.Click to see full answer. In this manner, how long does it take advil to start working? about 15 minutes Secondly, is it OK to give Children’s Advil every 4 hours? If the ibuprofen is swallowed and then vomited up later, don’t give your child another dose for at least 6 hours unless the dose was in tablet form and you can see that your child vomited up the whole tablet. Give every 6 to 8 hours as needed, but never give your child more than four doses in 24 hours. Similarly, it is asked, how long does children’s ibuprofen take to kick in? Ibuprofen comes in different strengths. The strength and dosage for your child depends on their age (and sometimes size), so always read the instructions carefully. Your child should start to feel better about 20 to 30 minutes after taking ibuprofen.Can I give my 10 year old Advil?Parents should know that there is no difference between medicine designed for adults and medicine designed for children as long as the dose used is appropriate. If you’re able to carefully dose the medicine appropriately, you can use adult ibuprofen tablets for children 3, 6, 8, or 14 years old.