A recent study out warns against over reliance on blood test for food allergies. I know I run several food allergy tests per week on both children and adults, so this article caught my attention. How can something that I use almost on a daily basis be considered useless, especially when I get clinical feedback of the drastic changes patients have seen in their health after removing specific foods.
One of the issues that comes up is there is no agreed-upon definition for food allergy. Is food allergy an anaphylactic reaction or can it be as simple as inappropriate response to the ingestion of a food. The human body can react to proteins, starches, other food components, a contaminant in the food (colorings, preservatives) or quite possibly some as yet unknown factor. There are several known adverse or toxic reactions to the ingestion of certain foods specific to each individual. These can manifest themselves by mental, emotional and physical disturbances characterized by confusion, fatigue, irritability, headaches, mucous congestion and other symptoms.
By definition, an allergy is an abnormal reaction to a generally harmless substance, occurring in a predisposed individual and caused by an antibody-antigen union. Immune-system mediated food allergy results from interactions between ingested antigens (foods), the digestive tract, histamine-containing mast cells and circulating basophils, and food specific immunoglobulins E (IgE) and G (IgG). IgE (immediate) and IgG (delayed) are the most common mediators of food allergy.
In the immunological sense, there are 4 different types of reactions. These include:
1) Type I- Immediate (less than 1 hour): igE antibody and antigen bind, resulting in the typical allergic reaction with problems such as sinus congestion, hives, bronchiolar constriction, and gastro-intestinal upset.
2) Type II- Cytotoxic Reactions: IgG or IgM to cell bound antigen leading to the destruction of the cell.
3) Type III- Immune Complexes: Antigens bound to antibodies (IgG immune complex), circulating in your blood stream, become deposited in tissues leading to tissue injury.
4) Type IV- Cell Activation: T-lymphocytes (another type of white blood cell) and allergen react with a mucosal surface and results in a delayed inflammation by stimulating sensitized T-cells. No antibodies are involved; examples include contact dermatitis, allergic colitis, and Crohn's disease.
You may now realize that adverse reactions to food are numerous and are usually more complex than conventional medicine's definition of allergy as an elevation of antibodies. Any bodily system can be affected by these adverse reactions, clinically, the digestive system, the immune system, the cardiovascular system, and the nervous system are the most frequently affected. Common clinical dysfunction includes intestinal cramping, constipation, diarrhea, hemorrhoids, Crohn's disease, colitis, congestion, inflammation, fatigue, hyperactivity, anxiety and depression.
Delayed food allergy does not appear to involve IgE antibody but rather IgG and less often IgM and IgA antibodies. Symptoms are delayed from 1 hour to 2-3 days after consumption. Because of the delay in onset of symptoms it is often difficult to associate the use of food with sensitivity symptoms. In addition, because of other factors, the response may vary from exposure to exposure. Food intolerances are far more common than many people believe. Many allergists believe that only a few people have food allergies. For them, there is a short list of foods of which cause only a few possible symptoms that are easily predictable. Those foods include wheat, dairy, corn, soy, chocolate, nuts, peanuts, eggs, fish, and perhaps tomatoes.
Methods of Diagnosing Food Sensitivity include but are not limited to the ones below.
- Radio Allergo Sorbent Test (RAST)
- Enzyme Linked Serum Assay (ELISA)
- ELISA/ACT (Enzyme enhanced Lymphocyte Blastogenesis Assay/Advanced Cell Test)
- Sublingual Test
- Scratch, Skin testing