Food allergies- could it be from proteins in food that cause food allergies?

Yes. It usually is a protein in the food that causes the food allergies. Protein, meaning the specific part of a food that triggers your immune system. For example: milk allergy may be because of the casein protein in the milk. There also may be allergies to the carbohydrate unit of the meats but that is rare and presents differently. Best be evaluated by an allergist to help you clarify your allergy.