After I removed gluten and casein, I discovered that other foods seemed to be causing a problem, like apples, soy, corn, tomatoes, and bananas. I see irritability, red cheeks and ears, and sometimes diarrhea or a diaper rash. I thought you said that these kids don't have allergies!
Many do have allergies, or allergy-related symptoms such as hay fever, asthma or eczema. Sometimes they have problems with foods which are not "classical" allergies, and which won't show up on skin tests. In this case, a different part of the immune system seems to be involved.