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What’s the Difference Between a Food Allergy, Food Intolerance and Coeliac Disease?

Food Allergies

Food allergies, food intolerances and coeliac disease are all becoming more and more common now-a-days and it can be confusing trying to understand the difference between them all. I have tried to describe each one in simple terms if you need help in knowing the difference.


Certain foods contain particular molecules (known as allergens), which are normally harmless, but can bring on an allergic reaction in certain people. When these allergens are ingested, the body mistakes them as a foreign body. The body then produces antibodies to fight off the allergen to try and destroy and neutralise it. During the immune response a number of chemicals are also produced; the main one being histamine. In allergy sufferers histamine is the chemical which causes most of the problem symptoms of an allergic reaction. Histamine can bring on a variety of symptoms including runny nose, itchy eyes, swelling of the lips, tongue and throat, wheezing and shortness of breath, a nettle like rash, inflammation, nausea, vomiting etc. In severe cases it can bring on an anaphylactic shock, the symptoms of which include throat swelling, severe asthma type symptoms and a drop in blood pressure and can be life threatening. Symptoms of an allergy often occur within minutes of coming into contact with the allergen.

The Top 14 allergens are gluten containing cereals, crustaceans, eggs, fish, peanuts, soybeans, milk, nuts, celery, mustard, sesame, sulphur dioxide, sulphites, lupin and molluscs.

There are 2 tests to check for a food allergy:

  • Blood test to check for the presence of raised antibodies

  • Skin prick test where a tiny amount of specific allergen is introduced onto the skin and a needle pricked through the drop of allergen on the forearm to see if it causes a reaction.


A food intolerance is when someone has a sensitivity to a particular food or has problems digesting certain foods. Typical food intolerances include problems with digesting lactose (sugar in dairy products), sensitivity to gluten containing cereals or an inability to digest high fibre foods such as beans and pulses. Symptoms of a food intolerance may include bloating, gas, migraine, nausea, vomiting, diarrhoea/constipation, joint pains, fatigue etc. Unlike an allergy, onset of symptoms can take some time to appear and does not involve the immune system.

Food sensitivity/intolerance can be down to a few different reasons:

Absence of certain chemicals or enzymes in the digestive tract means that the digestive system is unable to break down food properly. Undigested food then moves down the digestive tract causing problems.

Naturally occurring chemicals in food such as tea, coffee, chocolate and cheese can bring on digestive problems.

Naturally occurring toxins may be present in food such as chick peas and kidney beans if they are not cooked thoroughly.

Histamine occurs naturally in certain foods such as fermented products e.g. wine, vinegar, soy sauce, sauerkraut etc. and can cause food intolerance symptoms in some people. Other foods such as overripe fruit and incorrectly stored fish can have a build-up of histamine.

Food Additives such as those used in colouring, preserving and processing foods may cause problems with some people.

Because there are many different things that can cause a food intolerance the best way to identify what may be causing your symptoms is by following an elimination diet and keeping a detailed food symptom diary.


People with Coeliac Disease have a problem with ingesting gluten containing cereals including wheat, barley, rye and contaminated oats* etc. The presence of gluten can bring on diarrhoea, vomiting and bloating. The body also produces antibodies (different than those produced during a food allergy), which attacks the lining of the gut wall. If gluten is continually eaten, over time the lining of the gut wall becomes damaged and its ability to absorb nutrients is severely impaired. This can lead to weight loss, malnutrition, osteoporosis, anaemia, increased risk of cancer, miscarriage etc.

* Oats do not contain gluten but they become contaminated during the milling process. In some cases people with Coeliac Disease may still have a problem with gluten free oats as they are unable to tolerate the protein in oats called avenin.

Find out here how I can help you improve your digestive health.

Disclaimer: Always consult with your GP before embarking on any health regime.

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