Peppermint oil is an antispasmodic agent that is often used as a symptomatic pharmacological treatment in children with functional abdominal pain (FAP) or irritable bowel syndrome (IBS). However, the effectiveness of peppermint oil in capsules or in peppermints has not been evaluated appropriately in children. In this healthcare evaluation 240 children with FAP or IBS will be treated for 8 weeks with peppermint oil capsules, placebo capsules or ordinary peppermints. The effect on abdominal pain as well on secondary outcomes like quality of life, feelings of anxiety and depression, and schoolabsence will be evaluated;
