Understanding Food Allergies
In the last week alone, I have been asked by over a dozen people about food allergies in one form or another. It seems to come up in conversations quite frequently. What I've learned from these interactions is that there is a lot of misinformation, and a lot of questions about food allergies, what they are, and what it all means?
More than 170 food have been documented as causing true food allergies. Research estimates that 1 out of ever 13 children currently has food allergies.
Allergy, Sensitivity or Intolerance
I believe this is where the confusion often begins. The term food "allergy" is often misused, and/or over used.
This is how we categorize food reactions:
FOOD ALLERGY: (IgE) Immunoglobulin E response.
FOOD SENSITIVITY: (IgA, IgD, IgG, IgM) Immunoglobulin response
FOOD INTOLERANCE: Inability to Digest
True Food Allergies
True FOOD ALLERGIES are mediated by the IgE immune response. Most antibodies bind directly to the antigen and neutralize it, not IgE.
IgE structure is spider like, with branched legs. Some of these lets attached to the antigen, while others attach to Mast Cells. The IgE antibody destroys the Mast Cell, releasing histamine. The process also produces other byproducts, like inflammatory cytokines, lipid mediators, and proteolytic enzymes. These byproducts contribute to systemic inflammation and allergic reactions which may manifest as:
These reactions are immediate, typically beginning within minutes to hours after ingestion.
Food sensitivities are bit more complex, as they can involve any number of other immunoglobulin reactions. There are different Ig responses and different types of responses. These reactions are not characterized by histamine release, but can elicit some of the same symptoms through other mechanisms.
IgA: Specific to mucosal reactions in the GI tract. Their job is to fight bacterial and viral infections as they enter the mouth. Over time, as food reactions occur, IgA builds up causing intestinal/mucosal inflammation. These reactions are delayed and occur over long term exposure
IgD: Specific to the upper respiratory mucosal. Their job is to fight bacterial and viral infections as they enter the lungs. IgM antibodies can be converted to IgD, causing respiratory symptoms such as asthma. These reactions can be immediate or delayed depending on the mechanisms of action.
IgG: Specific to proteins in foods. These antibodies are associated with systemic exposure to large food proteins. Like IgE reactions, these are immune regulatory actions in response to unrecognized food particles...but without the destruction of Mast Cells. These reactions are associated with systemic symptoms and can mimic IgE symptoms
IgM: Specific to infections. These antibodies are associated with systemic exposure to bacteria, viruses or other infections. They are the first antibody produced during an infections. They make "memories" of antigens encountered for future recognition. This antibody activates complement C3d. They are immediate reactions as well as delayed reactions.
C3: This antibody is part of the complement system of the immune system. It's job is to enhance the actions of the immunoglobulins. This is a genetic variant that can increase the likelihood of food reactions, and/or the severity of reaction.
4 Types of Hypersensitivity Reactions
Sensitivities are the most complicated food reactions, as each body and each immune system is very unique and different in how it reacts to antigens. This is why the symptomology of systemic reactions is so vague.
Type 1 Reactions: This is an IgE reaction that occurs within 2 hours of consumption.
Type 2 Reactions (Cytotoxic Hypersensitivity): This is an IgG/IgM reaction that occurs 2 hours to several days after consumption. This occurs when antibodies bind to self-antigens or foreign antigens and leads to phagocytosis, killer cell activity, or C3 activation.
Type 3 Reactions (Immune Complex Mediated): This is an IgG reaction that occurs days to weeks after consumption. This occurs when your body is producing an abundance of IgG to a specific food. The IgG binds directly to the food as it enters the bloodstream forming circulating immune complexes.
Type 4 Reactions (Cell Mediated): This is not an antibody response. Individual cells, when coming into contact with an antigen, react by producing cytokines and inflammatory chemicals. This reaction occurs several days after consumption or exposure.
Immediate vs. Delayed Reactions
Immediate reactions are those that happen within the first couple of hours of exposure. These are the symptoms that we associate with IgE responses, but also be associated with mucosal Ig responses as well.
Delayed reactions are those that happen up to 3 days after exposure, and can last for up to 14 days. These are the symptoms associated with IgG and IgA responses.
Diagnosing Food Allergies
If food allergies are suspected, proper diagnosis is key in treatment. There are multiple testing options available depending on your symptom presentation.
Skin Prick/Scratch Test: This is the most common testing done through the Allergy Specialists. This test is performed by placing a small amount of a suspected allergen extract into a shallow scratch. Within 20-30 minutes a positive hive, or welt, will appear on the scratch. The size of the hive correlates with the intensity of the reaction. This test is used to diagnose IgE reactions only.
Intradermal Test: This is a similar test to the skin prick, but is more sensitive. This test is performed by injecting small amounts of a suspected allergen extract under the skin, rather than a scratch, and observing the reactions. These test results are more correlative with the serum testing. This test is used to diagnose IgE reactions only.
Elimination Diet: This method of diagnosis is not a blood or medical test, but a diet. In this diet, suspected allergenic foods are removed from the diet for a specified period of time. Then slowly added back in, one at a time, and observing the recurrence of symptoms. This can be a good diagnostic tool for children who are too young to do accurate serum testing, but may miss less common allergens.
RAST Test: This test is used in patients that are at risk for severe reactions when exposed, such as anaphylactic peanut allergies. This test is performed by blood draw. This test is used to diagnose IgE reactions.
Serum IgG1 Testing: This test is used to measure the delayed immune response. This test is performed by blood draw to measure immunoglobulin levels. This test can contain false positives due to cross reactions. This test is used to diagnose IgG1 reactions, which are less selective.
IgG4 Antibody Testing: This test is used to measure the delayed immune response to particular foods. This test is performed by blood draw to measure specific immunoglobulin levels associated with long term exposure to particular foods. This test is 90% accurate in diagnosing food specific autoimmune reactions. This test is used to diagnose IgG4 reactions, which are more selective and accurate.
IgA Testing: This test is used to diagnose new or active immune reactions in the digestive mucosa. This is performed by salivary testing. This test is used to diagnose IgA reactions.
Antigen Leukocyte Cellular Antibody (ALCAT): This test is used to measure leukocyte cellular reactivity in whole blood to food antigens, which measures delayed immune responses. This test is not a measure of IgG responses, but the final immune pathways. This test is more accurate than basic IgG testing in diagnosing food allergies.
ELISA Delayed Food Allergy Testing: This test is used to measure delayed immune responses (Type 2 and Type 3). This is performed by blood draw, where the serum is exposed to the antigen and processes are recorded. This test combines testing for IgG4 and other immune complexes. This type of testing is more accurate than measuring IgG1 alone.
Treatment for Food Allergies
At this time, the best course of treatment for food allergies is AVOIDANCE. The trick is learning how to properly avoid food allergens.
Many common food allergens, such as corn, are used in plastics, cosmetics, detergents, etc...making full avoidance very difficult. Others, like gluten, are complex and proper education on exposure sources is key.
Many people will say that they removed foods, but symptoms persisted, and this is because the hidden sources were not removed. It is best to consult a certified practitioner that is capable of guiding you in the proper journey.
Acupuncture can help to heal the damage caused by food allergies by increasing the body's repairative functions, decrease immune response, and balancing chemical process. This will only help if the trigger is removed.