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Food Allergies, Intolerances & Coeliac Disease

Cara Redpath Nutritionist


This blog has been written by our Nutritionist Cara Redpath to help understand and differentiate the different types of adverse food reactions:

If a food causes you harm when you eat it, this is known as an adverse food reaction. Adverse food reactions can be split into three groups:

  • Immune-mediated food allergy
  • Food intolerance or sensitivity
  • Coeliac disease

Within these conditions there are subgroups of different reactions depending on whether the immune system is involved in the reaction.

I have written this blog to help you understand the different types of adverse food reactions and explain how they work.

Immune-mediated food allergy

Definition of a food allergy

The medical definition of a food allergy is ‘an abnormal immune response to a food protein mediated by immunoglobulin E (IgE), non-IgE or mixed IgE/non-IgE immunological mechanisms’. Gosh what a mouthful! What this means is that a food allergy is an immune reaction to a protein in the food you have just eaten that your body has decided it doesn’t like.

How many people does it affect?

Food allergies effect 1-2% of adults and less than 10% of children.

What is the immune system?

The immune system is your body’s own private army against invaders that might come into it and cause it harm. The immune system consists of different kinds of white blood cells that seek out bacteria, fungi, viruses and other pathogens and effectively and swiftly neutralise and destroy them.

What happens to the immune system in a food allergy?

In a food allergy the body mistakenly identifies a protein in the food you have just eaten as an invader and mounts an immune response against it. It does this by producing antibodies to fight the perceived invader and destroy it.

The first reaction to an allergic food can often be mild however during this reaction the body becomes sensitised to that food. The next time the food is ingested the body is prepared and launches an IgE (type of antibody) mediated response to the protein in the food. This triggers the breakdown of basophiles and mast cells (white blood cells involved in the immune response) which triggers the release of histamine (the itchy scratchy, inflammatory chemical in the body) which causes the symptoms associated with a severe anaphylactic reaction such as swelling of the airways, tongue and body, hives and redness and itching.

After the initial severe reaction, there can be gastrointestinal symptoms that last for several days after the initial reaction. These can include stomach pain, vomiting, diarrhoea and bloating. There can also be lingering oral symptoms such as an itchy tongue and mouth.

Other types of food allergy

Food allergy can also present as a delayed IgG (type of antibody) reaction where the symptoms of an allergy occur days later in the gastrointestinal tract. These can include pain, vomiting and diarrhoea. Unfortunately, much less is known about the mechanism of this reaction and because of the delay in symptoms it makes it hard to diagnose and identify the triggering food.  

I like to think of this as the digestive system going in a huff a few days later because it remembers a playground fight it had at the beginning of the week and now its whole week is ruined.

Food intolerance or sensitivity

Definition of a food intolerance

A food intolerance is a non-immunological response triggered by a food or food component.

How many people does it affect?

Food intolerances effect 20% of the population.

What causes a food intolerance?

A food intolerance or sensitivity can be caused by various mechanisms related to under functioning of the digestive system. For example, lack of an enzyme such as lactase in a lactose intolerance or malabsorption of the food in the small intestine or nonspecific gastrointestinal malfunction that means you do not process or digest the triggering food properly.

I explain this to my clients by asking them to imagine their digestive system is a little overwhelmed and has a lot going on so starts skipping steps or doing a half-hearted job. When it does so, the digestive system starts to lose the skill to do the job properly in the first place.

 This can be the case for those who may suffer from IBS and struggle to digest the fermentable carbohydrates found in some FODMAP fruit and vegetable. This adverse reaction would be classed as a food intolerance.

The symptoms of a food intolerance can be limited to the digestive system only or a food intolerance may express itself as repeated migraine headaches, lack of energy or dark circles under the eyes.

When the digestive system is not working properly, it affects the whole body.

Coeliac disease

Coeliac disease

Coeliac disease is an adverse reaction to gluten.

What is gluten?

Gluten is a protein found in certain cereal grains such as wheat, spelt, barley and rye.

Why does gluten cause a problem?

Coeliac disease is a chronic health condition (meaning you have it for life) where eating gluten triggers an immune reaction leading to the destruction of the villi in the small intestine. The villi are tiny hair like projections in your intestine wall that help you absorb the nutrients from food. When they get destroyed in coeliac disease, this is known as villous atrophy.

The genetic connection

Coeliac disease runs in families and is found to be genetic in up to 20% of cases and therefore it is important to get tested for this disease if you have a first blood relative diagnosed with the disease.

What are the symptoms?

The symptoms of coeliac disease can present intestinally such as pain, bloating, diarrhoea, constipation and vomiting or extra intestinally such as stunted growth, migraine headaches, bone pain, muscle aches, repeated miscarriages and infections.

Non coeliac gluten sensitivity

Non coeliac gluten sensitivity is an intolerance to gluten that manifests in the same symptom pattern as coeliac disease, but the individual does not develop any antibodies against gluten nor is it an immune mediated condition. In other words, it is an intolerance to gluten that looks and feels very similar to coeliac disease but does not involve the immune system.

Final words

I hope this has provided a little more understanding on all the different kinds of adverse food reaction out there.

The best advice I can give is if a food causes you harm when you eat it, stop eating it immediately. If this food causes an anaphylactic reaction seek emergency medical help immediately and then care from an allergy specialist. If the food gives you unwanted digestive symptoms or you are unsure what is causing your unwanted digestive symptoms contact a Nutritional Therapist like myself. We have the experience and training to support you to establish the food that is causing harm and live a vibrant life without it without sacrificing nutrient intake.


You can contact Cara on and visit her website


This article is for information only and it cannot replace any proper medical care, if you or someone you care for seems to suffer from the described conditions or symptoms, then please seek professional help or speak to your GP.


Sources used for this blog:


Further information about Allergies, Intolerances and Coeliac Disease can be found: