When the immune system recognizes a foreign substance, it produces antibodies to fight off the allergens. IgG and IgE are two different types of antibodies produced in allergic reactions to food. IgE reactions are immediate and usually more severe, such as hives, swelling of the tongue and sudden diarrhea. IgG reactions are more common and more subtle and can result in many other delayed symptoms such as chronic pain, sinusitis, constipation, diarrhea, bloating, gas, fatigue and abdominal pain.