Food intolerances, sensitivities and allergies - what’s the deal?

Have you ever experienced unpleasant symptoms after eating certain foods, including sneezing, rashes, joint pain, bloating and diarrhoea? If so, then you might be wondering what is causing it.


These reactions to food can be divided into three groups: food intolerance, food sensitivity, and food allergy

Why knowing the difference matters

A food allergy has a much more apparent effect on your body straight after eating, such as a rash or, in the worst case, breathing difficulties. Oral allergy syndrome can cause such a drastic response. Whereas a food intolerance or sensitivity can be more insidious, and you might not notice symptoms for days. 

There are often overlapping symptoms resulting from these food reactions, so it is essential to distinguish between them as a food allergy can be life-threatening. In contrast, intolerances or sensitivities are more likely to cause chronic symptoms. 

One significant difference between the reactions involves the amount of food ingested that warrants a response. For intolerances or sensitivities, a substantial amount of food is often required to cause a reaction; however, food allergies can be triggered by a tiny amount of food, making them much more unpredictable and requiring urgent attention.  

Let’s look at the different types of food reactions in more detail. 

Food intolerance

A food intolerance is an inability to digest certain foods that result in symptoms including gas, bloating, diarrhoea, constipation, cramping and nausea. 

These symptoms may be due to a lack of required enzymes, reactions to food additives/preservatives like MSG and colourings or pharmacological factors such as sensitivity to caffeine, natural sugars or histamine.

A typical example is lactose intolerance. Lactose intolerance is caused by a lack of lactase in the gastrointestinal tract - the enzyme used to digest lactose, the sugar found in dairy. As you lack the enzyme to digest lactose properly, it stays within the large intestine where it is fermented by gut microorganisms which produce gases that cause discomfort. 

There is no medical cure for food intolerances, so avoidance is often best. However, in some cases, food intolerances result from an impaired gut function, such as leaky gut syndrome, an imbalanced gut microbiome or dysfunction of supporting organs such as the liver and pancreas. By healing the gut with diet and lifestyle changes, you may be able to reverse a food intolerance.

In the case of lactose intolerance, you can substitute many lactose-free products into your diet, including coconut and nut milk, coconut yoghurts, and vegan cheeses.

Food sensitivity

A food sensitivity reaction is typically caused by an imbalance in the gut, which affects the immune system. Increased intestinal permeability, referred to as ‘leaky gut syndrome’, is often a culprit. Food sensitivities can present in several ways, from dizziness, anxiety, headaches, difficulty sleeping, ear infections, fatigue, acne, and irritable bowel, to name a few. 

An elimination diet is an effective way to identify which foods are causing the sensitivities by removing a food type for at least a month and then reintroducing foods to see if symptoms arise again. 

Additionally, as with a food intolerance, a food sensitivity can ease over time with diet and lifestyle interventions by balancing the gut microbiome, supporting the function gut and improving immune health. 

Food allergy

A true food allergy involves a severe immunological reaction. The body's immune system identifies a food protein as a dangerous foreign body and produces IgE antibodies to fight it.  

Eight common food allergens account for the majority of allergic reactions, which includes: 

  • cows milk
  • egg 
  • fish
  • crustaceans
  • peanuts
  • wheat
  • soybean
  • tree nuts

Symptoms of a food allergy can range in severity from an itchy rash to severe anaphylaxis.

There is no medical cure for a food allergy, so strict avoidance is necessary. It is best to carry an epi-pen that supplies adrenaline and relieves anaphylaxis if there is contamination or exposure to an allergenic food. 

Why is coeliac disease different from food sensitivities?

Coeliac disease is an intolerance to the protein gluten found in grains, including wheat, rye, barley, semolina and bulgur. Many processed foods contain gluten, and cross-contamination may lead to involuntary ingestion. 

When you have celiac disease, eating gluten stimulates an inflammatory reaction. This reaction is different from other food intolerances because it involves the immune system (coeliac is an autoimmune disease). However, it is not a true allergy as it involves different antibodies (non-IgE), and there is no risk of anaphylaxis. 

There are commonly immediate unpleasant symptoms, including gut problems, joint pain and headaches, while eating gluten over a long time with celiac disease can cause weight loss and malnutrition. 

Coeliac disease affects 1% of the western population, and the only obvious way to treat it and relieve symptoms is to avoid gluten. 

Luckily, gluten-free products are becoming more common, making them easier to get ahold of and improving the quality of life of those suffering from gluten intolerance. 

Why it matters

It is essential to distinguish between food reactions to protect yourself from serious adverse effects. 

As mentioned above, food allergies can be life-threatening, whereas an intolerance or sensitivity is more critical to identify for long-term health and longevity. Therefore by determining which type of reaction your body is having, you will have clarity of the severity of the potential response and the long-term effect on your health.  

With this knowledge, you will be able to optimise your diet to suit your personalised needs so that you are not burdening your immune or digestive system unnecessarily.

How can testing help?

Testing and diagnosing a food allergy can be hard to accomplish as it involves many separate components in a hospital setting. However, testing for a food intolerance or sensitivity is more straightforward and can provide some peace of mind. 

Symptoms of a food intolerance can take time to appear, although tests can help confirm which foods are causing the problem. This way, you can be confident of which foods to avoid and reduce the accompanying discomfort. 

Food intolerance symptoms also overlap with other diseases such as irritable bowel syndrome, inflammatory bowel syndrome and stress. Therefore testing can identify whether food is the problem in the first place or whether you should seek help in other areas. 

There are a variety of tests available that identify different antibodies involved in inflammation that occurs after eating certain foods. 

Firstly, the Brunel food sensitivity test establishes the number of IgG antibodies produced through a finger-prick blood sample. The scaled level of response indicates the severity of the sensitivity. A low level of response to a particular food means it should be consumed in moderation, whereas a high level means the food should be avoided. 

A food sensitivity test is a quick, easy and accurate way of identifying personal trigger foods which can help optimise your food habits and guide an elimination diet, to help relieve chronic symptoms.

Alternatively, the more advanced Cyrex array tests address a more extensive range of issues concerning food sensitivities. The Cyrex panels detect both IgG and IgA antibodies to evaluate the immune reactions to food in its raw and cooked form, common food combinations, and reactivity to gum molecules and binding isolates. 

The benefit of this test is that it also considers food combinations about autoimmune disease, as certain foods may trigger autoimmune disease through a concept known as molecular mimicry. 

Molecular mimicry is the concept that may explain why the immune system starts attacking self-tissue in autoimmune diseases. Essentially, the “patterns” expressed on the surface of bacteria, viruses, and even plant viruses that stimulate an immune response have the same patterns reflected on the surface of your own tissue. Hence, the immune system starts attacking both, leading to tissue damage—more about this in other posts. 

If you want to find out more about food sensitivity testing, please contact The Autoimmunity Nutritionist Clinic. We offer Cyrex array panels and other food sensitivity tests so you can determine whether food is the culprit of your chronic symptoms. 

Also, be sure to join my free Facebook group, The Autoimmunity Community, to be supported by a network of strong-willed women living with autoimmune disease and chronic illness. 

The views expressed in this article are those of the author. All articles published on Nutritionist Resource are reviewed by our editorial team.

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London W1G & Harrogate HG1
Written by V. J. Hamilton, Autoimmune Disease Expert | BSc (Immunology), DipION, mBANT
London W1G & Harrogate HG1

After 25 years of suffering from multiple autoimmune conditions that affected her energy, skin, hair and joints, VJ discovered after studying immunology and Functional Medicine and training as a Nutritionist Therapist that by uncovering the root cause of her issues, she was able to transform her health, and now lives free of symptoms.

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