Food Foes: allergens vs sensitivities vs intolerances

  • March

    Deleterious reactions to many foods we eat are prevalent whether they are hidden or life threatening. Approximately 6% of children and 3-4% of adults have food allergies [1]. Those with food sensitivities and intolerances are more difficult to estimate. Some suggest that between 45-60% of people may be affected by IgG delayed hypersensitivities, but I would guess that everyone has at least one food that causes a heightened immune response at any given time [2].

    There is confusion about the differences between food allergy, sensitivity and intolerance. Many doctors and drug stores offer food allergy and sensitivity testings with confusing and sometimes skeptical results.

    This article will review:

    • Basic gut physiology and medical definitions
    • Food allergens, sensitivities, and intolerances
    • Antibody testing: pro’s and con’s
    • Common food aggravates
    • Hypo-allergenic diet: my favorite food sensitivity test
    • Reading grocery labels

    For all of the categories we will discuss, a healthy mucosal gut lining will protect your body from local and systemic injury. A healthy digestive tract includes maintaining a balanced gut flora of bacteria while avoiding excess refined sugars and pro-inflammatory foods.

    Significant inflammation of the digestive tract allows food antigens to pass through the gut mucosal membrane and into the blood stream where immune reactions and antibody production can occur. When mucosal cells divert from their tightly-packed formation we call this “leaky gut syndrome”. We can see some of the consequences of this condition when we look at Celiac disease.


    The lining of the stomach, small intestine and large intestine are made up of many layers: mucosa, submucosa and muscularis.

    These layers control digestion, nutrient absorption, and regulation of harmful toxins [3].

    The mucosa layer are actually folds of tissue covered with hairlike projections called villi that increase the surface size by 30-folds to maximize nutrient absorption. Each villi is lined with tightly-packed cells, tight junctions and each cell has even smaller microvilli among them (increasing the surface area by 600-fold), which only allows broken down nutrients to be absorbed into the blood stream. This layer is also responsible for local immune functions and regulating the microflora to protect the submucosal layer.

    The gastrointestinal mucosal lining is made up of many layers to stimulate digestion and protect toxins (and food particles) from reaching the blood stream. Photo credit: Britannica

    The gastrointestinal mucosal lining is made up of many layers to stimulate digestion and protect toxins (and food particles) from reaching the blood stream. Photo credit: Britannica

    The submucosal layer contains blood vessels that are the freeways to every part of the body (except the brain), including the muscles, nervous system and immune system of the spleen, bone marrow, thymus and lymphatic glands.

    For example, if a foreign particle (ie. toxic bacteria from the street meat you ate at last night’s game) enters the blood stream, antibodies will be created to that toxin and signal for your immune system to not only eradicate it, but also recognize it in case you have another craving for sausage at the game next week.

    The muscularis layer is made up of muscle tissue. It’s responsible for churning up your undigested foods and moving it along down your digestive tract.

    There are hundreds of enzyme reactions, mucosal immune responses, microorganism interactions (10×14) and digestive processes happening after every meal you consume. And they all happen without you being conscious of them.

    Before we discuss anymore, let’s first define a few key terms:

    • Mucous membrane – a layer of mucosal cells that form the lining of your digestive tract starting from your mouth and ending at your anus. This is a highly absorbable surface, which requires an effective immune system to regulate the environment
    • Allergen – any substance that causes an allergy reaction
    • Antigen – any substance that induces and antibody to be produced or released
    • Antibody – a large Y-shaped protein (aka. immunoglobulin, Ig) produced by the immune system upon exposure to a foreign substance/antigen. Antibodies are crucial for identifying pathogens (ie. bacteria or viruses) and signalling for your immune system to fight them off. There are 5 main immunoglobulins: IgM, IgG, IgA, IgE, IgD. We will discuss IgG and IgE in more detail
    • Enzyme – a diverse group of proteins capable of breaking down molecules into smaller subsets that can be readily absorbed by the body. It is often described as a “lock-and-key(s)” system where only unique molecules (ie. keys) can fit into the enzyme (ie. lock), which then allows catalytic reactions to occur

    Food Allergies

    • Type: IgE – Type I Hypersensitivity/ Anaphylactic
    • Nature: Clear cause and effect with rapid onset whereby mast cells and basophiles release histamine when exposed to an allergen and cause an inflammatory response (red, swollen, itchy) that varies from uncomfortable to life threatening
    • Timeline: Rapid spike of IgE that also tappers off relatively quickly. Specific IgE antigens have a half-life (amount of time for the original sample size to reduce to 50%) of 1-2 days in the blood stream,  however residual effects usually clear within 5-7 days but can last up to 2 weeks. Longer lasting or chronic symptoms are more often due to a delayed type III hypersensitivity response from IgG antibodies (we’ll look at this later)
    • Signs and symptoms: local and general inflammation to the skin (rash, hives, eczema, urticaria, atopic dermatitis), respiratory system (asthma, wheezing, restricted airflow), digestion (cramps, nausea, diarrhea)and vasculature (edema). It can be serious and even life-threatening as seen with anaphylaxis
    • Example: Seasonal allergies like hay fever and the common peanut allergy

    Researchers have found that IgE antibodies to egg are the earliest to be detected in infancy, followed by cow dairy antibodies. At infancy, rates of sensitization to food allergies are highest at 10%, then decrease to 3% by age 6.

    However, inhalant allergy sensitization developed much later. The rates of sensitization increasing with age from 1.5% at 1 years old to 26% by age 6 [4].


    Our bodies are designed to handle daily toxic exposures, in fact it is can be healthy to challenge your immune system and detoxification pathways. Living in a sterile environment has it’s dangers, especially with children.

    The body needs to maintain a balance between T-helper cells Th1 and Th2:

    • Th1 – is your “cellular immunity” that fights viruses and other intracellular pathogens, eliminate cancerous cells, and stimulate allergic skin reactions.
    • Th2 – drives your “humoral immunity” and up-regulate antibody production to fight extracellular organisms.

    It has been hypothesized that the decrease of infections (Th2) in Western countries and more recently in developing countries is at the origin of the increasing incidence of both autoimmune and allergic diseases (Th1). This is called the “hygiene hypothesis“. It is based upon epidemiological data, particularly migration studies, showing that subjects migrating from a low-incidence to a high-incidence country acquire the immune disorders especially with first generation.

    More simply:

    • Th2<Th1: If a child grows up in a clean, semi-sterile environment (low Th2) studies have seen an increase in autoimmune, asthma and allergic conditions (high Th1).
    • Th2>Th1: Alternatively, if a person is exposed to many micro-organisms, such as bacteria and parasite infections (high Th2), it has been shown to reduce allergic incidences (low Th1).

    Ideally, we should aim to have balanced Th1 and Th2 systems (Th1=Th2).

    Some exposure to toxins, micro-organisms and substances that challenge our immune system is crucial to find optimal health.

    Food Sensitivity

    Have you ever eaten a meal and within minutes or even hours it’s as if your body is bloated and being dragged down by bricks with your brain sludging inside your head unable to stay awake let alone think clearly? This delayed and often chronic reaction is due to IgG antibodies.

    • Type: IgG – Type III Hypersensitivity
    • Nature: Delayed onset with inflammatory cytokins and cascade of local and systemic events. These are mild, slower reaction that are cumulative and non-typical.  IgG reactions are often dose-dependent on the amount of a particular food is ingested.
    • Timeline: Food sensitivities are often difficult to diagnose with IgG antibodies produced after approximately 30 days after recognition of the food antigen. Once athreshold of IgG antibodies are made, symptoms begin 24-48 hours post-ingestion and IgG antibody levels rise slowly and linger for up to 3 months [6]
    • Signs and symptoms: Symptoms can vary from migraines, to cognitive ‘brain fog’, to behavioural difficulties in children with ADHD, to chronic digestive concerns (constipation, diarrhea, excessive gas, IBSIBD), to skin issues (acne, eczema, atopic dermatitis), to low energy, weight gain, water retention and joint pain
    • Example: Gluten sensitivity

    New research is being done to identify immediate IgG-mediated mast cell responses, which resemble IgE inflammatory anaphylactic reactions. However, IgG4 also has the potential to inhibit IgE histamine responses to help regulate inflammation from allergen exposure. Researchers are studying the effects of IgG immunotherapy for patients with atopic and digestive allergies [5].


    Celiac disease varies from a gluten sensitivity like an anaphylactic bee sting to a mild mosquito bite. To diagnoses celiac disease, a combination the following tests are commonly performed:

    • Anti-tissue transglutaminase (tTG- IgA)
    • Anti-endomysial antibody (EMA- IgA)
    • Anti-gliadin antibody (AGA- IgA)
    • Deamidated gliadin peptide antibody (DGP- IgA)
    • with a possible endoscopic biopsy of injured tissues

    Celiac disease is an autoimmune condition of the small intestine. In celiac disease, there is both an inflammatory conditions and a loss of microvilli in a portion of the small intestine.

    The loss of microvilli disrupts the mucosal cells and allows large molecules (ie. food) to pass through the tightly packed cells of the mucosal lining and into the blood stream where antibodies will be created to these ‘foreign bodies’. This is the same result as leaky gut syndrome. Now that the body has created ‘food antibodies’, the next time you ingest that food you will have an IgG response.

    Leaky gut syndrome allows large particles to pass through the tightly packed mucosal cells to enter the blood stream. Photo credit: Kitchen Stewardship

    Leaky gut syndrome allows large particles to pass through the tightly packed mucosal cells to enter the blood stream. Photo credit: Kitchen Stewardship

    Sometimes food particles have similar structures as molecules in your body and the antibodies can start to attack your own cells. This is called autoimmunity and can take on many different forms, such as:

    • Rheumatoid arthritis
    • Addison’s disease
    • Hashimoto’s thyroiditis
    • Graves’ disease
    • Multiple Sclerosis
    • Psoriasis

    Food Intolerance

    Often confused with a food sensitivity (or vice versa) is food intolerance.

    • Type: Non-immune specific
    • Nature: Lack of appropriate enzyme to breakdown a food into basic units that are able to be absorbed by the gut lining and used for physiological activities by the body
    • Timeline: Sudden initial reaction within 30 minutes of ingesting aggravating food. Effects can last a few hours
    • Signs and symptoms: explosive diarrhea, excessive gas, low energy and fatigue, dehydration, malnutrition
    • Example: Lactose intolerance, but could also be casein or ovalbumin sensitivity. If taking lactose-free products or lactase enzymes while consuming dairy products still creates uncomfortable symptoms, it may be another protein you’re intolerant to, or more likely a food sensitivity.

    Antibody Testing

    Food Allergens – IgE:

    When it comes to general allergies, the skin-prick test using common allergens is the ‘gold standard’, while IgE and specific antibody blood testings are available to confirm digestive allergens.

    • In vivo (in/on the body) – allergen skin-prick tests (Gold Standard)
    • In vitro (in a lab) – IgE blood sample with venipuncture

    For topical or inhaled allergens, skin-prick tests are ideal. A series of common allergens are dotted along the skin to see which produced a histaminic reaction (ie. a swollen patch around the insult).

    However, for digestive allergens I prefer using IgE blood tests.

    Food Sensitivities – IgG:

    Food sensitivities on the other hand also measure for an immune system antibody however it is a different form called IgG.

    • In vivo (in/on the body) – muscle testing or energetic tests
    • In vitro (in a lab) – IgG blood sample with finger prick

    Muscle testing, applied kinesiology, and energetic tests are controversial. The idea is that the patient holds a vial of a food antigen and the body will weaken in strength if there is a sensitivity. Physical strength is manually tested by the practitioner, which offers a level of conscious and unconscious bias. There are also various energetic tests that measure a person’s response to the potential trigger food.

    I also have issues with the current IgG tests and often find them to be unreliable. I know colleagues who have sent in multiple tests of the same blood sample to different lab companies and even the same labs with varying results. Some patients have even shown to be highly sensitive to foods they have never eaten before.

    Until IgG tests become more accurate and reproducible, I still prefer taking a more practical approach to identifying potential food sensitivities with the hypo-allergenic diet (we’ll take a closer look at this test later in the article).

    Food Intolerance – Enzyme challenge

    Meanwhile, a food intolerance occurs when the body doesn’t have the correct enzymes to breakdown the food particle into it’s basic components.

    There are specific test to identify food intolerances, such as the lactose tolerance test.

    Common Food Aggravates and their Family Members

    Using a diet diary (click here for my free template) to identify your personal negative responses to food aggravates and the families they belong to will help you become more aware of your body’s response, food choices and your optimal health.

    • Most common food allergens: egg, dairy, wheat, corn, soy
    • Tree nuts: peanuts, pecan, pistachio, pine nut, coconut, walnut
    • Seafood: crab, lobster, shrimp
    • Brassica/ Cruciferous family: broccoli, cauliflower, cabbage, mustard plant, brussel sprouts, bok choy
    • Night shade/ Solanaceae family: potato, tomato, eggplant, peppers
    • Proteins from many tropical fruits: pineapple, papaya, mango, kiwi

    Once you are aware of your current eating habits and reactions, using a food challenge will confirm food aggravates and your personal reactions. I recommend the hypo-allergenic diet as a tool to identify and test your food sensitivities.

    Hypo-Allergenic Diet

    I completed my first hypo-allergenic diet in my 3rd year of medical school. It was challenging but insightful. Never in a million years would I have guessed a major food sensitivity to be SOY.

    Being Chinese, my family is used to eating a lot of soy products: soya sauce, tofu, fermented bean curd, edamame, miso, soya nuts, soya milk. I knew that I was sensitive to cow dairy and when I switched from cow milk to soy milk I was still experiencing bloating, gas, stomach pains, and fatigue. It seems obvious looking back now, but at the time I never imagined someone with a Chinese background could have difficulties ingesting soy.

    Hypo-Allergenic is also known as Oligoantigenic or Elimination diet.

    This means that we avoid eating the most common ingredients that cause people inflammation and digestive issues. IT IS NOT A DIET TO LOSE WEIGHT. It should be viewed more as a food sensitivity TEST.

    As mentioned previously, the top 5 offenders include: wheat, dairy, corn, soy, and eggs.

    Note that some of the foods on the list are very nutritious, so if you are not sensitive to the food, bring them back into your diet (ie. eggs).

    Also remember, many non-gluten or non-dairy foods may not be healthy. Just because they remove those ingredients does not mean they haven’t replaced them with other poorer quality ingredients.

    Try and stay away from packaged, canned, processed and deep fried foods. And be cautious of dehydrated and dried foods for they often contain added sugars and preservatives. Raw and fresh is often your best bet for optimal health.

    To get your free comprehensive Hypo-Allergenic eManual including dietary guidelines, recipes for a 7-day meal plan, shopping lists, and food re-introduction schedule, sign-up HERE.

    A thorough elimination and re-introduction is not easy, which makes the IgG blood tests more appealing to many. The hypo-allergenic diet takes 6-8 weeks to fully complete with lots of meal planning and having the people you live with (and possibly cook for) on board. If a full hypo-allergenic diet is not plausible for you at this time, you can modify the test by eliminating one food at a time. Use a re-introduction schedule to keep track of your sensitivities:

    1. Eliminate possible food aggravate for 3 days
    2. On the 4th day, eat 3 servings of that food
    3. If you have no change in symptoms, wait another couple of days while keeping your other foods consistent before moving on to the next food
    4. If you do have an aggravation, avoid eating that food until you have tested all your food sensitivities and only eat it in limited amounts


    Read Your Labels

    Whether it is a food allergen, sensitivity or intolerance, make sure to read your labels carefully. There are many hidden ingredients not only in your pre-packaged, prepared, canned or frozen foods but also your supplements. Avoid the common self-prescribing mistakes that end up having people feeling worse rather than more healthy and vibrant.

    1. Choosing products based on price
    2. Asking health store workers for recommendations
    3. Using Dr. Oz or similar shows or magazines to self-prescribe
    4. Using the directions on the bottle for recommended dosages
    5. Not reading labels
    6. Thinking “natural remedies” are all safe
    7. Not tracking your progress or having a re-evaluation date
    8. Relying on supplements instead of food
    Supplementing your diet for is a great addition and not a substitution for a healthy, varied diet.

    Supplementing your diet for is a great addition and not a substitution for a healthy, varied diet.

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This website is NOT to be used as a diagnostic or treatment tool. Always consult with your Conventional Medical Doctor or Naturopathic Doctor for specific concerns. In cases of medical emergencies visit your nearest hospital or call 9-1-1.