Diseases, Nutrition
Do you react to foods?


Food allergies and food sensitivities became more prevalent over the past few decades. Some common food reactions keep raising. It certainly has a lot to do with the way we live (stressed, overstimulated), with the quality of foods and drinks we consume (processed and toxic), the air we breathe in (polluted) or the cosmetics, detergents we use. These factors can make us more vulnerable and susceptible to all sort of maladies. Our bodies have to work hard to process everything from surrounding us environment and ingested foods, to stay in balance and to provide our bodies with what it needs for optimal functioning. When our body is overwhelmed our immune system and other parts may overreact inducing food reactions.

Reactions to foods we may experience include:

  • Psychological reactions (exorphins present in wheat/gluten and diary/casein bind to opioid receptors within our body influencing our brain, our behavior)
  • Toxic reactions (food contamination or food poisoning)
  • Immune-mediated reactions such as food allergies and food sensitivities (type I, II, III, or IV hypersensitivity)
  • Food intolerance reaction (enzyme deficiency)

There is often confusion around what is what and sometimes “allergy”, “intolerance”, and “sensitivity” are used improperly, which may  depend on naming convention as well as on how you look at the reaction to foods; whether you look at the reaction itself or symptoms it causes. Without going into depth and complexity of these reactions, I describe below the key differences.

What are they?

Let’s focus here only on two immune-mediated reactions (IgE & IgG) and food intolerances. Be aware that a person may also experience a combination of food reactions after ingesting one food, which may involve an immune reaction and non-immune reaction, cell-mediated food reactions.

Generally, we can distinguish:

  • immediate and often severe immune responses to IgE antibodies for food allergies
  • milder and delayed immune responses to IgG antibodies for food sensitivities
  • metabolic or gastrointestinal responses caused by a lack of enzymes or other inability to digest certain foods for food intolerances

Food allergies (IgE mediated) are associated with immediate-type gastrointestinal hypersensitivity, oral allergy syndrome, acute urticaria and angioedema, allergic rhinitis, acute bronchospasm, and in severe reactions anaphylaxis. Some symptoms include: reddening of the skin (hives, itching); swelling (lips, eyelids), tightness of the throat; impaired breathing; vomiting; or diarrhea. Most of these symptoms appear right after eating the offending food, for example nuts, fruits, raw vegetables, eggs, diary, or chicken. A person is always aware of symptoms and reaction to the allergenic food. In some people it’s a lifelong reaction whereas in others it disappears.

Food sensitivities (IgG mediated) involve delayed (hours, days) allergic-like responses/hypersensitivities that can last for days. The mechanism is based on triggering an immune system by producing IgG antibodies after a repeated exposure to a food antigen. The reaction can be dose-dependent and often involves common foods. Some delayed food sensitivity symptoms can include fatigue, abdominal pain, bloating, vomiting, diarrhea, asthma, joint stiffness, swelling and pain, skin itching, rushes, hives, psoriasis, memory disturbances, behavioral changes or fever. A person is not always aware about having this food reaction as it can be difficult to connect a particular food reaction with its delayed symptoms. It disappears weeks/months after elimination of a trigger food.     

Food intolerances are associated with an inability (often genetically determined) to break down particular food compounds caused by a lack of enzymes or their low expression. This type of reaction does not directly involve the immune system and in some individuals response can be dose-dependent. It typically causes abdominal cramps and pain, diarrhea, bloating, sometimes headaches. The most frequent food intolerances include lactose intolerance, histamine intolerance, or fructose intolerance.

Do reactions to foods have health consequences?

Exposure to foods causing allergic, intolerance reaction or food sensitivities can be a contributing factor in many health conditions such as arthritis, eczema, psoriasis, depression, anxiety, migraine headaches, muscle pain, chronic fatigue, as well as in inflammatory bowel disease (IBD) or irritable bowel syndrome (IBS). So if you have chronic health complaints it is worthwhile to give your food reactions a closer look.


There is a number of ways to test for food reactions and the methods become more sophisticated to meet the growing demand. Different tests are appropriate depending on the immunologic reaction a person is trying to discover. Most common methods include elimination/challenge, skin testing, patch testing, ELISA antibody tests for IgG, IgE, IgG4, and IgA antibodies, biochip technology, and energetic testing methods. Each and every method has its advantages and disadvantages and particular methods investigate only a specific aspect of food reactions. For some people, laboratory testing results can be a great motivational trigger to promote dietary changes serving as a “proof” that a particular food is reactive. Also tests can be recommended to people unwilling or unable to do an elimination diet or for those who can’t easily identify the food related responses. Elimination diet you can do on your own and it is in principle very easy but it takes the time and diligence and can be overwhelming whereas an accurate and reproducible food allergy test allows nutritious foods to remain in a patient’s diet while removing offending foods. If you want to do some testing discuss possibilities with your health care professional. Below I provide the principles of an elimination diet.

Elimination & Challenge Method

The most common solution currently available is to begin identifying potential sensitivities by following an elimination and challenge of the specific foods. The basic idea is to eliminate a suspect food for a period of time to see which symptoms subside and then reintroduce it to see which symptoms reappear.

How to do it:

  1. Eliminate a single suspect food, group of foods (for example nightshades) or the 10 most common food allergens (milk, eggs, wheat, grains, soy, shellfish, peanuts, tree nuts, sugar and alcohol) for a certain period of time (from days to weeks or months)
  2. Reintroduce one food at a time for three days, eaten 1-3 times a day (Note: this type of testing should not be done with foods known to cause a severe or anaphylactic reaction).
  3. Keep a diary to record how you feel for up to three days after a food is reintroduced. Some reactions may appear 24-72 hours after food consumption.
  4. Follow the same steps for each food.

a)  If a food causes a reaction such as brain fog, fatigue, itchy skin, stool changes etc., then eliminate it. Wait with introducing a new food for two-three days.

b)  If you don’t have a reaction, preferably leave that food temporarily out of your diet and put it back into your diet at the end of the food-reintroducing phase.

The food elimination/challenge approach can be time-consuming, carries a risk of producing a severe reaction (especially for IgE-mediated food allergies), can be difficult to reproduce, coincidental factors may affect the outcomes and it may result if false negatives. Therefore, it’s good to have some background info before applying this or any other testing approach.


  1. “Adverse food reaction and functional gastrointestinal disorders: the role of dietetic approach” F. Pasqui et al. J Gastrointestin Liver Dis, September 2015 Vol. 24 No 3.
  2. “Food allergies” Wendy Hodsdon. Natural Medicine text book, fourth edition. J. Pizzorno & M Murray. Elsevier 2013.
  3. “Testing for food reactions: the good, the bad, and the ugly” G. E. Mullin et al. Nutrition in Clinical Practice, Vol. 25 No 2, 2010.
Category: Diseases, Nutrition icon February 2 2017
Dr Joanna Krzeslak-Hoogland
Author: Dr Joanna Krzeslak-Hoogland

Being inspired by the effect of nutrition, lifestyle and mind on our health, I am dedicated to help people on their journey to wellbeing.

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