<<Disclaimer: Verify this information before applying it to your situation.>> If someone has confirmed celiac disease and gets a bout of diarrhea I think the most likely reason is gluten. Looking very closely at the diet in the days before the event may explain the diarrhea. If everyone in the family have had diarrhea then it is more likely to be infectious. If there are several episodes of diarrhea happening say every month that is too often for infections, somethings in the diet. Joe Murray Not medical advice to be used in individual situations. More like general information. Individual problems need discussion with a personal physician.