Have you considered trying a probiotic?
I give mine a half-teaspoon of InLiven Probiotic Superfood daily, but you would probably need to start with 1/8th tsp and gradually build up to one teaspoon, preferably 2x/day.
In most cases, food allergies/sensitivities result from an inability of the digestive tract to break down the proteins contained in the foods. Probiotics help restore the bacterial balance of the digestive system and aid the digestive process by helping to break down proteins, carbs and fats more efficiently. A natural result of this the reduction (and in most cases, elimination) of diarrhea, constipation and vomiting.
And like Tylan, it's great for humans too.