Do you have a physical reaction when you eat certain foods or food groups? Are you therefore avoiding these foods because you’re “allergic” to them? But is it really a food allergy or is it a food intolerance?

I’ve seen this over and over and all too often, it’s a self-diagnosis based on symptoms that arise after eating these foods. From experience, a food intolerance can result in the same symptoms as a food allergy and it is therefore very easy to confuse the two.

How does your body react to a food allergy vs a food intolerance?

Whilst a true food allergy will affect the body’s immune system causing a reaction that can have a widespread effect, in some cases severe (eg hives or wheezing) or even life-threatening (egs an anaphylactic reaction), a food intolerance on the other hand, will cause symptoms that are generally less serious and more often than not, digestive problems which then cause discomfort. Nausea, vomiting, brain fogginess and skin reactions such as eczema as well as respiratory problems are common reactions as a result of a food intolerance. It may be that you are able to eat a small amount of a food that you know can cause you problems in which case, this is a food intolerance rather than an allergy.

Within the body, the immune system reacts differently in each scenario. With a true food allergy, IgE antibodies are produced in response to consumption of the offending food and these antibodies are then responsible for the symptoms that then develop. With a food intolerance, the immune system has different responses; IgA or IgG antibodies are produced rather than IgE antibodies.

Whilst it is important to establish the cause of these symptoms, it is also important to understand that it may not be an actual food that has caused these symptoms.

It is clear that a food allergy can have devastating consequences but it is also important to be aware that food intolerances can develop into more serious health consequences over time. It is therefore not only important to establish to cause of these symptoms, but it is also important to understand that it may not be that actual food that has caused the symptom.

There is evidence to suggest that IgG and IgA-mediated food intolerances are related to gut permeability and this is often seen in cases of Crohn’s disease and other gut conditions. Essentially, if the gut is not healthy, larger gaps develop within the intestinal wall lining, a condition known as Leaky Gut, which allow larger, undigested food molecules to escape into the blood stream. These are then identified by the immune system. This immune reaction then causes allergy like symptoms such as rashes or digestive symptoms such cramps, diarrhoea or constipation.


The foods that cause these IgA or IgG responses can be very difficult to identify through a medical test (as opposed to a food allergy IgE response which is more definitive)

So what’s the best way to deal with food intolerances?

In many cases that I see, avoiding a food group often means over compensating with another food or food group and this over consumption may not necessarily be a better (let alone healthier) alternative. For example, if you’re avoiding gluten, you may be replacing this with high sugar processed gluten free alternatives. This will have a detrimental effect on your gut health which in itself will cause similar symptoms to those associated with an intolerance.

In the majority of cases that I see, focusing on improving the compromised gut health can have a profound effect and in many cases will ease the symptoms significantly if not completely.

Poor gut health in general will result in similar symptoms to food intolerance symptoms

Essentially, if the food you eat is being properly digested, it will pass through the digestive tract efficiently and will not be allowed to pass through the tight junctions within the gut lining. The food will be broken down effectively, starting in the stomach and passing through to each section of the digestive system, fully absorbing nutrients back into the body, before being efficiently eliminated with regular bowel movements.


Let’s take a look at some of the common causes of food intolerance reactions:

  • Unhealthy Gut Microbiome

It is important to ensure a healthy balance of good vs bad bacteria. Eating more fibre will help the good bacteria to thrive whereas reducing sugar will starve the bad bacteria.  Eating fermented foods such as sauerkraut and probiotic yoghurt will also introduce good bacteria and help to restore a healthy gut.

Very often, this will be diagnosed as Irritable Bowel Disease which is an umbrella term for Irritable Bowel Symptoms such as wind, bloating, cramps, diarrhoea and constipation.

READ MORE: Fermented foods – what are these and are they worth the hype?

  • Stress

This is one of the biggest factors that is often overlooked. In times of stress, the digestive system becomes more sluggish and thus is not able to efficiently process the food you eat. The food therefore does not pass thought the digestive tract as quickly and efficiently as it should and is more likely to fester, giving off gases and harmful bacteria that then in turn cause symptoms such as wind, bloating and stomach cramps.

Solution: Aim to eat mindfully, taking the time to chew the food as thoroughly as possible, so the food reaches the stomach in a state where digestion has already begin (in the mouth with saliva) to help the process overall.


  • Enzyme Activity

It may be that there is an absence of an enzyme needed to fully digest a food; a common one is Lactose intolerance where there is a lack of the Lactase, the enzyme needed to digest the milk sugar lactose.

Solution: A digestive enzyme supplement containing lactase can be taken with a a meal to aid digestion.


  • Lack of Stomach Acid

For efficient digestion, the stomach needs to be highly acidic, so that the stomach digestive enzymes are activated. If there is too little acid, digestion will be impaired.

Solution: Starting the meal with a small salad with an lemon or vinegar based dressing will provide an acidity boost to help with digestion. Alternatively, you can consider a digestive enzyme supplement containing a stomach acid before a meal to prepare the stomach.


  • Food Sensitivity

Foods that have been processed or preserved will contain additives that can trigger symptoms. For example, sulphites used to preserve dried fruits can cause asthma attacks in some people

Solution: Read food labels carefully to avoid know food triggers but better still, try to eat foods that have been minimally processed.


  • Coeliac Disease

Coeliac disease involves an immune reaction to gluten, the protein found in wheat. Those with a true allergy to this protein will develop severe digestive discomfort immediately after eating even a trace of gluten. However, in absence of an allergy, those who eat too much gluten, over the long term can develop chronic digestive symptoms due to an unhealthy digestive system as a whole

Solution: Coeliac Disease can only be determined following a test, in which case it must be avoided completely. Cooking from scratch to ensure you know exactly what is in the food you are eating is best or choosing good quality ready made alternatives that you can trust to be labeled gluten free.


Without a diagnosis, focusing on healing the gut and improving digestive health is key. Reducing gluten significantly will ease the burden on the gut to allow it to heal.


Is it Worth Testing?

There is a lot of controversy surrounding testing based on identifying the IgA and IgG antibodies. It may be that these show up in test results simply as a result of eating certain foods and not necessarily proving a significant intolerance. Cooked vs raw foods can also result in different outcomes.


If symptoms appear within a few minutes of eating a particular food, it is highly likely that this is due to an allergy. If the cause is unknown, my approach is in the first instance, is to keep a food and symptoms diary to identify any patterns and correlation. To do this, remove the suspected foods for a minimum of 2 weeks  and then reintroduce them one at a time. If a reaction reappears or symptoms develop, it is likely that this food is the culprit and can therefore be avoided.

If symptoms are severe, then avoiding all together is preferable. This does not necessarily mean forever; focusing on a gut repair program to ensure a healthy and efficient digestive system may mean that in time, the gut will be more robust and able to tolerate food intolerances.


If you are looking for a reliable test, I would recommend and use the Cyrex labs tests whose range of tests can identify gluten or gluten related allergies as well as a number of other food sensitivities.


The bottom line

  • A food allergy occurs when the body’s immune system is activated to a harmless food
  • A food intolerance occurs when the body reacts to a particular food
  • The symptoms of both may be similar and can range from mild to moderate but a food intolerance does not cause a severe life-threatening response
  • Improving gut health and integrity is key as well as avoiding foods that are known to cause reactions as far as possible to ease the burden

Were you aware of the differences between a food allergy vs a food intolerance and how your body reacts? Let me know in the comments below.