[header] How to diagnose food intolerance [title] Pay attention to the timing of your symptoms. [step] If you have a food intolerance, you won't see a reaction to the food you eat right away. A food allergy will result in a more immediate reaction. 
[substeps] Digestive symptoms caused by a food intolerance usually come on gradually over the course of a couple of hours. A food allergy usually results in symptoms almost immediately.