Food sensitivities occur over time after the GI tract begins to break down (becomes "leaky") and poorly digested food particles enter into the lumen of the intestine. The immune system identifies these leaked food particles as foreign invaders and marks them with an antibody, much like a flag, so they can be eliminated. Since the immune system is highly specific, the next time the offending food is consumed and hits the taste buds, the immune system is activated. This process is different from having a food allergy (true genetic allergy) but the offending foods must be identified and removed from the diet for a period of time while the gut is repaired. My Food Sensitivities - 44 Foods identifies 44 of the most common foods consumed in standard diets so problematic foods can be properly identified.