By Nancy Mehlert, MS
In collaboration with Mila McManus MD
In this article, you are going to learn a lot of medical lingo. This is a very important topic and we’re confident you’ll get through it!
The human body has a highly complex, multi-faceted system to defend it from outside threats or harm. We refer to it as our immune system. Immunoglobulins (Ig) are one part of this system and are a diverse group of proteins that protect the human body against disease. Another term used for immunoglobulins is antibodies. In reference to allergic reactions, you may be familiar with Immunoglobulin E, or IgE, and Immunoglobulin G, or IgG. When we ingest a food and these immunoglobulins incorrectly identify that food as foe rather than friend, an adverse symptom (or group of symptoms) results, which we call a food allergy. Some of the most common food allergens include cow’s milk, chicken eggs, wheat, soy, corn, legumes (e.g., peanuts), fish and shellfish. The common theme to responses are inflammatory symptoms including vasodilation which leads to swelling, tissue damage, increased vascular permeability (which allows substances to leak out of blood vessels), and the release of chemical mediators.
IgE is primarily found attached to mast cells. IgE allergies can be very serious and cause symptoms such as difficulty breathing, swelling, hives or even anaphylactic shock. IgE antibodies, once exposed to the allergen (aka, in this case, the food triggering allergic response), cause the release of histamines and other chemicals which cause symptoms such as itching and inflammation. Commonly these reactions are immediate upon ingestion of the allergen, occurring within minutes. Testing for this kind of allergy is done by skin prick or blood test and treatment is usually to block the release of the histamines with medications, and avoidance of the allergen.
IgG is important for building immunity even as a baby grows in its mother’s womb. These antibodies build long term resistance to infections, toxins, bacteria and viruses. IgG allergic reactions do not release histamine and thus do not respond to a skin prick. In fact, these allergies are often called “delayed onset” allergies because immediate symptoms are less common. Rather, symptoms can take hours and even days to manifest and repeated exposure to the same allergen can be cumulative in nature because it takes much longer for the body to clear/reduce the IgG after exposure to the food when compared to clearance rate of IgE. The degree and severity of symptoms can also vary because of the genetic makeup of the individual. Symptoms can range from headache, nausea, seizures, hyperactivity, joint pain, fatigue, irritability, and cognitive dysfunction, to skin rashes and mood disorders. IgG reactions have also been associated with auto-immune diseases such as Hashimoto’s thyroiditis, Rheumatoid arthritis, and lupus. It is well understood that a significant portion of our ingested food proteins reach the lymphoid tissues (clusters of immune cells) in the gut where ideally the intestinal immune system can discriminate proteins in the food stream as innocuous (harmless) and not of any pathogenic (disease-causing) importance. However, if the mucosal barrier integrity is lost, this lymphoid tissue loses its ability to distinguish friend from foe, causing tolerance for certain foods to be lost. This often occurs with the foods eaten most frequently and repeatedly. Digestive problems play a major role in the development of IgG food allergies as a result of intestinal lining integrity being compromised by a poor diet or the use of antibiotics, steroids, artificial sweeteners, and medications such as NSAIDS (non-steroidal anti-inflammatory drugs). We call this “leaky gut”, and this allows food particles to enter the bloodstream where they are recognized by the immune system as a perceived threat that triggers an immune attack. Chronic attacks keep the immune system hypersensitive and overworked, leading to poor performance and weakening of the immune system. Treatment for IgG reactions includes avoidance of reactive foods and restoration of gut integrity. It is possible, but not guaranteed, that a person can later resume eating the foods in moderation. Since the antibodies are cumulative with IgG reactions, the frequency with which you eat the food will determine how quickly the antibodies rise again to the level which triggers symptoms again.
The Clinical Relevance of IgG Food Allergy Testing Through ELISA by Raymond M. Suen, and Shalima Gordon, US Bio Tek Laboratories Copyright 2003
A Critical Review of IgG Immunoglobulins and Food Allergy- Implications in Systemic Health by Raymond M. Suen, and Shalima Gordon, US Bio Tek Laboratories Copyright 2003