How much is too much? Well, it depends on the person.
So how much gluten is too much? This is a question with a highly individualized answer. People who have celiac disease (officially diagnosed or not), even a minuscule amount of gluten can trigger a reaction, which will cause a tremendous amount of damage to the small intestine in the majority of patients. A portion of patients, approximately 22%, will have significant damage done to their small intestine but will not actually feel any of the gastrointestinal symptoms. For healthy patients, the amount of gluten intake to trigger symptoms varies greatly from case to case. The only way to test this is to individually test it, which is a risky chance to take.