In a food reaction, the immune system reacts by releasing cells called antibodies. Foods that cause antibodies to be released are called antigens or allergens. Two types of antibodies commonly produced in response to foods are IgE (immunoglobulin E) and IgG (immunoglobulin G). Food allergies and food sensitivities differ by the type of antibody produced and the speed of the reaction. Food allergy is an immediate reaction caused by the production of IgE antibodies, while food sensitivity is a delayed reaction caused by the production of IgG antibodies to specific foods.