Eating egg on toast could lead to food sensitivity reactions

I recently spoke to a GP friend who said that almost everyone she sees in clinic is not eating one thing or another because they have self-diagnosed an “intolerance”. Though it is tempting to just dismiss this as an increase in faddy eating, fuelled in part by social media – could it be that taking some foods out from your diet can actually make you feel better? Quite possibly – but should you stop there? The questions that are less frequently addressed by Dr. Google, are why are you reacting to that food in the first place, and is there something that you could be doing to help improve your tolerance and get you back to eating a full and varied diet (which my GP friend might argue is the best idea for long term health). (Spoiler: there may well be foods that you need to continue to avoid, but the aim is to broaden your dietary horizons).

First, let’s go back to the beginning. What type of food reactions are there and what do they involve?

Allergy and food sensitivity

Everyone is well aware of allergy and the potentially fatal consequences if things go wrong – and research from 2007 showed a 500% increase in food allergies in the UK since 1990 (1). Allergies occur when your immune system recognises a normally harmless protein from food or pollen for example, and launches an immediate response using IgE antibodies. This then leads to a release of histamine which is responsible for the allergy symptoms like runny nose, swollen lips, itching, tummy ache, vomiting, or difficulty breathing.

Food proteins can also trigger an immune response via other types of antibodies (namely IgG, IgA and IgM). These often lead to a delayed response, with symptoms such as digestive discomfort, itching, headache, joint pain, fatigue appearing any time up to around three days. This can make it much more difficult to identify what the triggers are – the gold standard approach for doing this is an elimination diet, followed by a challenge with the suspected culprit, though blood testing can also be useful, particularly if you are reacting to large numbers of foods. There are several common offenders, dairy, soya, corn, gluten/wheat and egg. This could partly be on account of how often we are exposed to these ingredients, alongside the modification of some of them through hybridisation and processing.

These non-IgE mediated food sensitivities are more likely to occur if you are not digesting your food properly, and you have a disrupted gut lining so large particles which should remain in the gut (which is essentially outside the body) can get through and activate underlying immune cells. Gut infections or an imbalance in the bacteria living in your digestive tract can also play a role, as over time they can affect how your immune system works and reduce your ‘tolerance’ to food proteins.

Gluten sensitivities

Gluten is one of the commonly vilified food components – it even made it into ‘Groundhog Day: The Musical’ as a possible explanation for why Phil Connors was reliving the same day over and over. Coeliac disease affects around 1 in 100 people in the UK, though according to Coeliac UK, only around 30% of these has been diagnosed. Though digestive symptoms are common, symptoms can range from a rash (dermatitis herpetiformis) to problems with movement and coordination. Others may have no symptoms at all, and be dubbed ‘silent’ coeliacs. Coeliac UK have introduced an online assessment that you can use to find out if asking for a screening test would be worthwhile.

Wheat contains gluten and can cause food sensitivities
Coeliacs need to avoid wheat, barley, rye and spelt. Oats can often be tolerated but they need to be gluten-free certified.

As with allergy and food sensitivity, coeliac disease also involves an aberrant immune response, though in this case exposure to gluten leads to autoimmune destruction of the gut lining. Life long removal of gluten (even trace amounts) is the only treatment approach, but in some people even this is not enough to relieve symptoms: They may find they are reacting to other foods, often those that contain proteins which have regions that look remarkably similar to proteins in gluten, and the intestinal damage incurred prior to diagnosis could make this more likely to occur.

Non-coeliac gluten sensitivity, can also lead to symptoms inside and outside of the gut. It is not completely clear whether people who feel that gluten is responsible for their health concerns are actually reacting to gluten, another protein in wheat or the fermentable carbohydrate it contains, but either way, the removal of wheat/gluten improves symptoms (2). In many cases the immune system appears to be involved (3,4)

Food intolerances

An intolerance – though often used in common parlance to describe a non-IgE mediated hypersensitivity reaction – actually doesn’t involve the immune system at all. It is caused by the reduced capacity of the body to break down a particular nutrient or chemical, and the subsequent overload generates symptoms.

Lactose intolerance, where people lack sufficient lactase enzyme to break down the milk sugar can lead to digestive upset. Damage to the gut lining where lactase resides, is one cause of temporary lactose intolerance, and this is often seen in people recently diagnosed with coeliac disease.

Histamine intolerance on the other hand can lead to symptoms that look like allergy (the raised histamine is the common factor). Excess histamine may not just be a result of an intolerance however, eating too many foods rich in histidine (which is converted to histamine internally), having excessive histamine-creating bacteria in your large intestine or having a permeable gut lining that histamine can traverse (which can often happen with gastrointestinal inflammation) can also cause issues (5).

Salicylates, which are naturally found in foods and also in aspirin,  can also lead to a pseudo-allergic reaction, which as with histamine intolerance has many of the same symptoms as allergy, but doesn’t involve IgE antibodies. Many people who react to aspirin also react to the food additive tartrazine.

How can nutritional therapy help?

As you can see, there are many different ways in which we can react to foods, and getting to the bottom of what is going on is the key to improving your health. In some instances, removing the offending food for good is the only option (think allergy and coeliac disease), whereas in other cases taking all reactive foods off your plate may not be the best approach, as you could be left with a very limited dietary repertoire, which in the long term can deplete the variety of microbes in your gut leading to a greater likelihood of reacting to other foods.

Once you know what is going on, delving deeper into why you are responding in this way can pay dividends. As with much in functional medicine, many issues are linked to the health of your gut. If you can work to improve this, you may find in time that your symptoms reduce and your tolerance increases. Tending to your resident gut bacteria by eating a wide variety of plant foods is a great start. Your ability to digest may also need support. Are you chewing your food, for example?

A plate of rainbow coloured vegetables to support gut health
Support your gut bacteria and reduce inflammation with plant foods

Your capacity to detoxify may also be critical. If you don't have the nutrients required to support the detoxification of histamine, for example, it is much easier for your system to be overwhelmed. Some people have genetic variants that mean they have increased requirements for some of these vitamins and minerals. For all of us, dietary protein and vitamin B12 are highly important, as are leafy greens for folate. Are you getting enough?

Lastly, the robustness of your immune system could be worth addressing:  Why is it so quick to react to potential threats? Several nutrient deficiencies, including vitamins A and D, zinc, magnesium and selenium, as well as stress and inflammation could be at play here. What you eat can either increase or decrease inflammation (think oily fish and fruit and vegetables, versus fizzy drinks and processed meat), so reviewing your diet is always a good first step.

In most instances, improving your health long term is not as straight forward as just changing one thing, each system might need some attention.

If you think that one or more foods don’t agree with you, and would like to find out if nutritional therapy could help identify your triggers and/or reduce your sensitivity, then email me at to arrange a free 15 minute discovery call.



  1. Gupta et al., (2007) 'Time trends in allergic disorders in the UK', Thorax, 62(1), pp.91-96. Available at:
  2. Barbaro et al., (2018) ‘Recent advances in understanding non-celiac gluten sensitivity’, F1000Research, 7, F1000 Faculty Rev-1631. Available at :
  3. Hadjivassilou et al., (2016) ‘Neurological dysfunction in coeliac disease and non-coeliac gluten sensitivity’, The American Journal of Gastroenterology, 111(4), 561–567. Available at:
  4. Losurdo et al., (2018) ‘Extra-intestinal manifestations of non-celiac gluten sensitivity: An expanding paradigm’, World Journal of Gastroenterology, 24(14), 1521–1530. Available at:
  5. Reese, I (2018) ‘Nutrition therapy for adverse reactions to histamine in food and beverages’, Allergologie select 2(1): pp.56-61. Available at:

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