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One of the basic premises of food allergies is that a reaction is
not always immediate.  In fact, it can take up to 72 hours for
a reaction to show up although it is very difficult to pin a reaction
72 hours later on one food you ate three days ago.  We've seen
reactions that can be directly attributed to food 10-14 hours later
(like tomato sauce eaten at dinner causing a bad tantrum at school
the next day).
 
I don't know if celiac reactions can be that delayed since gluten
reactions are not due to "allergies."
 
Jean Jasinski