<<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.