A food allergy is an adverse reaction to a food or food component that involves the body’s immune system. A true allergic reaction to a food involves three primary components: 1) contact with a food allergen 2) immunoglobulin E (IgE-an antibody in the immune system that reacts with allergens); and 3) mast cells (tissue cells) and basophils (blood cells), which when connected to IgE antibodies release histamine or other substances causing allergic symptoms.
There are also some adverse reactions to foods that involve the body’s metabolism but not the immune system. These reactions are known as food intolerance. Examples of food intolerance are food poisoning or the inability to properly digest certain food components, such as lactose or milk sugar. This latter condition is commonly known as lactose intolerance.
You may want to try the elimination method, drop one thing at a time, I.E. lactulose products from your diet and see if the sx disappears.
Of course you may always return to an allergist specialist who has methods of identifying the foods you are allergic to or intolerant to. Reference: Medical-Surgical Nursing, 9th Edition, Brunner-Sardath.