you are what you eat. If you eat things that your body cant handle of digest you will have a symptom. Depending on the severity and the immune system depends if it is an allergic reaction or just a sensitivity. Most health problems stem from your diet so it is great you are looking into that. If you immune system is working at full capacity it can keep allergens at bay, but if it is busy with other things then it cant handle all the allergens and you have a reaction. Any reason your childs immune system would be being affected? Did you notice symptoms worsened after a virus or live virus vaccine? Good luck and hope you are able to control things without medication ASAP!