Your body builds up resistance to toxins after awhile. Think of yourself in a situation with a potent allergen. If you're allergic to cats and have no cats in your house, spending an evening at a family member's house with 4 or 5 cats would likely cause misery - itchy eyes, runny nose, rashes on your skin, etc. But if you were to get a cat, you'd eventually build up a tolerance to that allergen, and overtime, it would seem to subside.
It sort of works that way to gluten and other mildly toxic foods. After awhile, most people will build up some form of tolerance, which is why there are so many gluten-sensitive people out there that don't know it. They just get used to the side effects, and they fade overtime as your body adapts. However, once you get off of it and you feel great, you get used to a whole new feeling of health and your natural resistance fades away. Then, when you slip up, it hits you like a ton of bricks.
I have no real food intoleranes worth mentioning, but I can't digest grains like I used to. If I go out on the rare occasion and eat something I don't normally eat, I'll be met with gas and less than ideal digestion where I never had that problem before. Primal makes you healthier, but your resistance to toxic food will slowly wear away so when you do slip up, it's an unpleasant experience.
And that is the TRUE purpose of grain toxins - to make you feel ill. We are so used to consuming "food" that isn't real food, we don't even know we're sick!!!
Don't put your trust in anyone on this forum, including me. You are the key to your own success.