88 Food Allergy and Sensitivity TEST (FAST) (IgG, C3d/C3b, IgE, IgG4) - Serum

Overview:

Various Antibodies and Their Meaning

IgE (immunoglobulin E) allergies are the immediate responses to a foreign substance that has entered the body via food or inhalation. IgE allergies can cause very serious symptoms like difficulty in breathing, swelling, and hives. In more serious cases, IgE reactions can lead to anaphylactic shock. Our test measures the blood level of IgE, one of the five subclasses of antibodies. Antibodies are proteins made by the immune system that attack antigens such as bacteria, viruses, and allergens.
They can become confused or cross-reactive and begin attacking foods instead. High titers of IgE are associated with allergic reactions, which is when the immune system overreacts to environmental antigens such as pollen, pet dander, and/or parasitic infections.
 
IgG (immunoglobulin G, total) are antibodies that provide long-term resistance to infections and have a much longer half-life than an IgE allergy. This food sensitivity can be more subtle, and many people live with it for years, if not their entire lives. Sensitivity symptoms range from fatigue, headache/nausea, seizures, hyperactivity, bloating, mood changes, or dark circles under the eyes. IgG symptoms typically occur within 3-72 hours after the offending food was ingested and they will create ongoing inflammation that can make most conditions worse. Because they can present at such varied times, it is hard to isolate from a diet history alone, and testing becomes particularly useful.

The degree and severity of symptoms vary greatly from person to person because of genetic makeup. The complete elimination of IgG positive foods may bring about important improvements in symptoms of irritable bowel syndrome, autism, ADHD, cystic fibrosis, rheumatoid arthritis, and epilepsy, as demonstrated in numerous clinical studies. It is important to get tested for food sensitivities to know what foods work for the patient’s body and what foods don’t. If you are only looking at allergies, or IgE, then you would miss the IgG mediated symptoms, creating an incomplete patient picture.
 
IGG4 (IMMUNOGLOBULIN G SUBTYPE 4): is another antibody produced in the body to fight infection.  Desensitization injections, or allergy therapies, increase IgG4 to help neutralize the reaction of IgE. This is because of its potential to decrease histamine responses by blocking IgE from attaching to receptors, causing degranulation. Levels of IgG4 are beneficial up to a point, as they block IgE or allergic reactions and result in immune tolerance to
foods.  

Too much IgG4 causes immune-mediated conditions, known as IgG4-RD that typically a?ects multiple organ systems in the body. For these reasons, it's important to know the levels of IgG4 in the body to be able to maintain a correct balance. An example of a tissue that is susceptible to higher levels of IgG4 is the esophagus, resulting in Eosinophilic Esophagitis. IgG4 also interferes with the thyroid, contributing to autoimmune thyroiditis, and can also cause IgG4- Related Diseases (IgG4-RD) of the ovaries and prostate.