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  • Jan Clementson

Are food reactions causing your health problems? The low-down on food allergies and intolerances

Food reactions leading to health symptoms are a growing concern. Back in 2009 a review paper estimated such sensitvities to affect around 20% of the population, although many reports are suggesting a big increase in incidence since then. Post-pandemic this figure is likely to be significantly higher. As we come out of the throes of covid, we are seeing a big inflammatory picture emerge leading to an explosion in food sensitivities. I am seeing this emerging picture in my nutrition clinic, as well as the student nutrition clinics that I supervise. And this picture is being reflected in the demand for food intolerance testing, with the food intolerance testing companies struggling to keep up with demand. Let's take a deeper dive into this to see how it might be affecting you.

Food Allergy vs Food Intolerance

A food allergy is not the same as a food intolerance, although some of the symptoms may be similar. Sometimes, It can be very difficult to differentiate between a food allergy and an intolerance. A food allergy involves a specific and immediate immune IgE antibody response, whereas a food intolerance stems more from a delayed IgG antibody response or a non-immunological cause relating to the gastrointestinal terrain. This can include impaired digestion and malabsorption, enzyme deficiency (especially lactose), changes in the structure or microbial composition of the gut, or reactions to toxins of plant, bacterial or fungal origin.

Categories of Food Reactions

Food Allergies (IgE reactions) - Type 1 Allergy

These are what are termed "classic allergy reactions". Generally speaking, food allergies have more severe symptoms and can be acute or life-threatening in the case of anaphylaxis. It can take up to 7-10 days of exposure to the sensitising food before an allergic reaction occurs. However, when it does occur it happens quickly and is more severe. But the prevalence of true food allergies is very low at around 2-5%. The majority of food reactions fall into the less-severe food sensitivity and food intolerance categories.

Common symptoms include:

  • Skin rashes (urticaria)

  • Swelling of the eyes, lips, mouth, throat, tongue, voice box or face

  • Constriction of throat and breathing difficulties

  • Nausea, vomiting, diarrhoea with abdominal bloating

  • Dizziness and low blood pressure

90% of all Type 1 food reactions involve dairy, eggs, peanuts, wheat, soy, fish/shellfish, tree nuts (walnuts, cashews, almonds), corn.

If you suspect that you have a severe reaction to certain foods, it would be advisable to check this out with your GP who can test you for a food allergy.

Food Sensitivities (IgG reactions) - Type 3 Allergy

A review article by Mullin et al, 2010, linked the symptoms associated with food IgG immune reactions to a consequence of enhanced absorption of food antigens from the digestive tract into the blood resulting in a systemic production of IgG antibodies. This is the "leaky gut" scenario whereby the intestinal walls have become compromised allowing partially digested food that should remain in the digestive tract to pass into the blood. Because the food has not been broken down properly into its constituent parts, the immune system does not recognise the food particles and mounts an immune response as though they were "foreign' molecules.

Common symptoms include:

  • Digestive - abdominal pain, bloating, nausea, vomiting, diarrhoea &/or constipation

  • Systemic - sweating, fever, chills, weakness, fatigue, reduced emotional tolerance

  • Joints/muscles - food-allergic arthritis, pain, stiffness, swelling

  • Skin - itching, rashes, hives, redness, swelling, scaling, thickening

  • Lungs - food-induced bronchitis & asthma

  • Brain - brain fog, lack of concentration, memory disturbance, behavioural problems

Food sensitivity symptoms tend to be less severe or acute but can become chronic. Reactions can begin within 15 minutes or within a few hours after eating but are often delayed by up to 48 hours or longer and can last for hours or days, making it very difficult to pinpoint the offending food. Invariably, there can be more than one intolerance, which reflects imbalances in the gut terrain. The food antigen-immune complex is ordinarily removed by immune cells (macrophages) in the spleen and liver but if there is an overload of the food antigen or where there is poor immunity, these complexes can be deposited in tissues leading to the wide range of symptoms.

Cross-Reactivity Reactions

To complicate things further, foods can cross-react with non-foods such as pollen, dust mites, animals or even your own body tissues. Where your immune system attacks a body tissue instead of a problematic food, it can be because they have a similar molecular structure. This can lead to an autoimmune type reaction. Here's an example of how a gliadin (gluten) molecule has a similar chemical composition to the cerebullum in the brain, which can lead to the immune system attacking the brain in a person sensitive to gluten.

Food Intolerances - Non-Immune Mediated

These type of reactions do not generate a specific "memory" immune-antibody response but instead activates the non-specific immune response of the body's innate immune system. This is a generalised 'first line of defence' mechanism that the body uses to protect itself from any general threat, rather than a "memory response" to a specific antigen. This type of response is often elicited as a result of:

  • Impaired digestion and malabsorption

  • Lack of or reduced enzymes for digestion - e.g. lactose, fructose, histamine

  • Imbalanced gut microflora (dysbiosis) - toxic microbial by-products

  • Chemical effects - caffeine, medications, food additives, heavy metals

  • Toxin reactions - from plants, bacteria, fungus/yeast/mould, parasites

  • Recurring/chronic stress or psychological factors - disrupt gut balance

Gut terrain plays a big role here. As the terrain becomes more imbalanced, the gut becomes more inflamed leading to loss of tolerance to more and more foods, impairment of the gut barrier and subsequent systemic IgG reactions. In this way, a person's diet can become more and more restrictive.

Common symptoms of food intolerance

These can vary and potentially affect many systems but most often they involve the digestive system, skin and respiratory system.

  • Diarrhoea &/or constipation

  • Bloating

  • Abdominal pain

  • Nausea

  • Headaches

  • Rashes

  • Runny nose

  • Acid reflux

  • Skin flushing

Top Common Problematic Foods

  • Dairy - especially lactose but also to dairy protein such as casein or whey

  • Eggs - this is especially common

  • Gluten - found in grains such as wheat, rye, barley, oats

  • Caffeine - coffee, tea, chocolate, energy drinks

  • Salicylates - spices (curry, paprika oregano, mustard, cayenne, pepper), sultanas, raisins, oranges

  • Histamine - fermented foods such as yoghurt, sauerkraut or aged foods such as cheese

  • Sulphites - wine, beer, dried fruit, sulphite preservatives in packaged goods

  • Yeast - baked goods (bread, biscuits, muffins), fermented foods, stock cubes or gravies

  • Food preservatives and colourants - such as tartrazine (colour) or aspartame (sweetener)


Food Reaction Types

If you have had a severe reaction to any food, consult your GP about getting tested for a food allergy reaction. If you have not had a severe reaction but suspect one or more foods may be problematic for you, consider doing a food elimination diet.

Food Elimination Diet

This is considered the "gold-standard" when it comes to addressing food reactions. It is much easier to do if you already know or suspect which foods are problematic. However, it can become quite difficult to implement if you don't know which foods are problematic and can lead to a very restrictive diet and potential nutrient deficiencies. If you do not know which foods are problematic, consider taking a food intolerance test.

  1. Eliminate the suspected foods from your diet for 3 months - it takes around 23 days for the IgG antibodies to reduce by half. 3 months allows for a significant reduction of the antibodies, although it may take up to 6 months for them to fully clear.

  2. Support your gut during this period to help improve your gut conditions - chew your food slowly; be mindful when you are eating; use lemon juice and bitter foods to stimulate your digestive juices; increase your fruit and vegetable intake to feed your good bacteria; try a gut-calming herbal tea such as peppermint, slippery elm or marshmallow; consider taking a digestive enzyme to help support food breakdown.

  3. Address your stress - try out different techniques such as deep breathing, relaxing music or gentle exercise. Consider changing thought, emotional or behaviour patterns that may be contributing to your stress.

  4. Re-introduce foods after 3 months (if symptoms have subsided) one food at a time - start with one food for 7 days. Monitor your symptoms. If no problems, reintroduce the next food for the next 7 days, and so on.

  5. Symptom flare-up upon re-introduction - remove the offending food and continue with the elimination diet for another 1-2 months. Focus on improving gut health before attempting re-introduction.

  6. Re-try re-introduction - follow the same process as before.

Food Intolerance (IgG antibody) Tests

These take the guesswork out of food reactivities and makes the elimination process much easier to implement; and without resorting to a restrictive diet that can be difficult to follow and potentially lead to to nutritional deficiencies. These tests also have the advantage of flagging up random foods that you would never have suspected were causing you a problem. There are many such tests on the market today. As with any product, some are better than others. You want to choose a product developed by a good diagnostic lab with a track record of expertise that follows the developing research in this area and integrates the latest research into their testing procedures. Look out for test results that numerically identify the reactivity level of each food. This really helps when many food reactions flag up, which is often because the gut barrier has been impaired and partially undigested food is leaking into the blood. Removing the top 5 reactive foods in such cases can make a big difference to reducing the inflammatory response and allow you time to work on healing your gut.

YorkTest Premium Food Intolerance Test

YorkTest is one of best IgG food intolerance tests on the market. With over 40 years of diagnostic testing in this areas, they have honed their product. It's a simple home test kit with a finger-prick blood draw, so no need to consult your doctor for a blood draw. Finger prick blood draws are not appropriate for all blood tests for several reasons. However, YorkTest attests to the stability of the IgG molecule for such a test and have repeatedly shown reproducible results. Hence, this is one of the food intolerance tests that I do recommend. Here's the link to the product if you wish to try it.


Expert Help

Does this feel a bit too overwhelming for you? Would you like some expert help in addressing your food reactions? You are not alone. It can be a total minefield. I have been there. It is because of my own food intolerances that I became a nutritionist. But I am here to tell you that you can overcome these - just like I have done - and return to a normal life. Let me help to guide you through this process. Book your free 30 minutes telephone Discovery Call to find out how I can help you.

More Information

Maybe you are not ready yet to take the plunge. Maybe you want to read around this area and acquire more information on how nutrition can help with your symptoms. And that is ok. We all have to work at our own pace and when then time is right for us. If you want to keep abreast of information in this area, click on the link below.


  • Baenkler HW. Salicylate intolerance: pathophysiology, clinical spectrum, diagnosis and treatment. Dtsch Arztebl Int. 2008 Feb;105(8):137-42.

  • Lin J, Sampson HA. The role of immunoglobulin E-binding epitopes in the characterization of food allergy. Curr Opin Allergy Clin Immunol. 2009 Aug;9(4):357-63.

  • Mullin GE, Swift KM, Lipski L, Turnbull LK, Rampertab SD. Testing for food reactions: the good, the bad, and the ugly. Nutr Clin Pract. 2010 Apr;25(2):192-8. doi: 10.1177/0884533610362696. PMID: 20413700.

  • Zopf Y, Baenkler HW, Silbermann A, Hahn EG, Raithel M. The differential diagnosis of food intolerance. Dtsch Arztebl Int. 2009 May;106(21):359-69; 3.


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