Allergy Awareness
What Allergy?
Allergy is the most common chronic disease in Europe (EAACI, 2016). The UK has some of the highest prevalence rates of allergic conditions in the world, with over 20% of the population affected by one or more allergic disorder. (M. L. Levy, 2004) and in the 20 years to 2012 there was a 615% increase in the rate of hospital admissions for anaphylaxis in the UK (Turner, Paul J., et al, 2015). However, up to 90% of presume food allergies are not actually allergies - we also need to think about food sensitivities and food intolerance’s as well!
What is our immune system meant to do?
Your immune system controls how your body defends itself. If you are allergic to a food, for example peanuts, your immune system recognises peanuts as an invader, or allergen and over-reacts. An allergic reaction usually causes symptoms in the nose, lungs, throat, sinuses, ears, lining of the stomach or on the skin. The immune system can have several different types of response depending on the antibodies that are being used for the response e.g. IgA, IgE, and IgG.
These antibodies are produced by our immune system in response to contact with certain foreign substances such as a virus or bacteria. Our body will make antibodies against these invaders to fight them off. Foreign substances may also be things like pollen, fungus spores, animal dander, dust and different foods.
If you have an adverse reaction to food, it will either be mediated by our immune system or it will be non-immune related.
If it is mediated by our immune system it is usually a response by IgE or IgG antibodies. An IgE response is usually life long and may potentially be fatal. An immune response that is mediated by IgG antibodies is not life threatening and may even be reversed.
Allergy Cascade
How do we develop allergies?
If we develop an allergy, the body will have been exposed to something that tells it to create an immune response. That something would be an allergen, it may be something we swallow, get injected by (bee sting), touch or breathe in for example.
When an allergen gets into the body of someone with a predisposition (inherited) to that allergen, their B-lymphocytes (a type of white blood cell) will produce a specific antibody (IgE) against the perceived foreign substance (allergen) in order to get rid of it from our body. The specific IgE antibody will only be able to recognise that allergen.
Everyone makes IgE, but those who are prone to allergic reactions tend to make larger quantities. Allergies are majorly influenced by genetics.
Mast cells (living in tissues all over the body), have receptor cells that will recognise the IgE antibody and allow them to bind to their cell surface. Once the person is again exposed to the same allergen, they will bind to the IgE antibody which is on the surface of the mast cell.
If two allergens bind next to each other it will cause the cell membrane to break down and release chemicals such as histamine. There are 30 different chemicals that can be released in response to an allergen. The release of these chemicals is known as an allergic response, and causes us the symptoms we experience when having an allergic reaction, this could be itchy skin, eyes, swelling, wheezing etc.
What is a Food Allergy?
A food allergy is an adverse exaggerated immune system response to a food protein which causes the body to trigger an allergic reaction. The typical symptoms experienced usually involve several systems; the dermatologic (skin and skin derivatives), respiratory (nose, pharynx, larynx, trachea, bronchi and lungs), gastrointestinal (mouth, esophagus, stomach, small and large intestine, anus), cardiovascular (heart, blood vessels and the blood), and/or neurologic (brain, spinal cord, and peripheral nervous system) systems
It can be classified into IgE-mediated and non-IgE-mediated reactions.
IgE-mediated food allergy
These type of food allergies, as described in the Food Cascade diagram above, will cause your immune system to react abnormally to one or specific foods e.g. egg, wheat, nuts etc. This type of reaction will cause symptoms quickly (minutes to a couple of hours).
Anaphylaxis is the most severe symptom that an IgE-mediated food allergy can cause and initial treatment would be to inject with epinephrine.
In order to manage these type of food allergies, you need to strictly avoid the foods/ substances that cause reaction. Family and friends need to be educated in order to help you and emergency medications should be carried. Recently the baby weaning guidelines have been changed and it is now encouraged to introduce babies (4-6 months) to peanuts in order to help prevent peanut allergy development. There are also promising trials for future treatment of these types of food allergy which include oral immunology.
Non-IgE-mediated food allergy
According to The Royal Children’s Hospital Melbourne, “Non-IgE mediated food allergies are caused by a reaction involving other components of the immune system besides IgE antibodies. The reactions do not appear immediately after the ingestion of the food and usually relate to reactions in the gastrointestinal tract such as vomiting, bloating and diarrhoea.”
Non-IgE-mediated food allergies include a wide number of disorders such as allergic proctocolitis, food protein-induced enteropathy, celiac disease and Heiner syndrome, although with some of these disorders there is a favourable prognosis, with most cases resolving in the first few years of life. We have much more information on the mechanisms of an IgE-mediated allergy than non-IgE-mediated allergies. This is probably due to it being very difficult to confirm a diagnosis as well as these types of allergies having very varied symptoms at different sites of the body. In general these types of food allergies are not life threatening.
What we do know, is that the non-IgE-mediated food allergies involve the immune system but not via IgE antibodies. Other cells that may contribute include T cells, B cells, mast cells, macrophages, and eosinophils. The products that these cells then produce may involve responses from even more cells such as our epithelium cells, our nerves and our fibroblasts . The interactions are very complex!
Food allergy can be confused with food intolerance, which does not involve the immune system.
There are 14 major food allergens but you can be allergic to any food substance.
The top 14 food allergens are listed below, but the most common ones are milk, eggs and peanuts:
Celery
Cereals containing gluten
Crustaceans
Eggs
Fish
Lupin
Milk
Molluscs
Mustard
Tree Nuts
Peanuts
Sesame seeds
Soya
Sulphur dioxide (sometimes known as sulphites)
What is a food Sensitivity?
Food sensitivities, will have a much more delayed response (hours to days) than a food allergy but will still trigger the immune system. The sensitivities do not have to be permanent, and they usually do not stimulate the release of histamine because the immune system response will be to create IgG antibodies instead of IgE antibodies. IgG antibodies will not directly break down mast cells.
This type of food sensitivity (IgG-mediated food intolerance) is believed to be caused by gut dysbiosis, namely an increase in a person’s gut permeability.
For those people who also have intestinal permeability (leaky gut), when undigested food particles enter their bloodstream the immune system will react as follows:
IgG antibodies will bind with a perceived allergen (undigested food particles) which will then create a coating, becoming an immune complex. This complex now triggers additional immune responses such as the release of pro-inflammatory cytokines which can cause inflammation and potentially damage surrounding tissues. If intestinal permeability is not improved, the immune reaction will be constantly activated and may result in an overloaded immune system, resulting in chronic inflammation.
This type of overloading can be seen in migraine cases as well as IBS, chronic fatique syndrome and Crohn’s disease.
There are various symptoms experienced with this type of immune reaction, such as rashes, urticaria, joint aches, headaches as well as asthma symptoms. IBS symptoms will include including diarrhoea, abdominal cramps and constipation. As mentioned above, this type of immune response is delayed and accumulative. Symptoms such as these may not be experienced for days to months.
What is a Food Intolerance?
Non-immune mediated reactions to food will fall in to several categories including digestive disorders, pharmacological and toxic reactions plus .A food intolerance is an adverse reaction to a food that does not involve the immune system. Reactions can be immediate or delayed up to 20 hours after a food is eaten but they are not life threatening. According to the NHS, “the number of people who believe they have a food intolerance has risen dramatically over recent years”. However, often people think that they have a food intolerance but the true cause of their symptoms is something completely different.
enzyme deficiencies
This is where there is an absence or insufficient levels of specific enzyme/s which are needed in order to properly digest food. An example may be a lack or insufficient levels of lactase which breaks down lactose (milk sugar). This may then result in an intolerance to milk with symptoms such as stomach ache, diarrhoea, bloating and increased gas.
pharmacological reaction e.g. tyramine, phenlethylamine, caffeine
Some people are more susceptible / react more to certain chemicals such as amines found in some cheese or caffeine in tea and coffee. This category will also include reactions to colourants such as tartrazine, preservatives such as sodium benzoate and sulphites, flavourants including monosodium glutamate and aspartame. This highlights the importance of enjoying less processed foods and more whole foods!
Microbial products
This includes histamine. Intolerance to histamine does not mean that you are sensitive to histamine. It highlights that you may have developed too much of it. Histamine is important for our body to function but we can only take so much of it in our body. If we are eating a lot of histamine rich foods, such as fermented foods, dried fruits, processed foods and vegetables including aubergine and tomatoes plus aged cheese or we are unable to break it down effectively (DAO deficiency) then our levels may increase causing various symptoms. These symptoms include headaches, fatigue, digestive issues, nausea and sinus issues etc. Eating food low in histamine may help your symptoms as well as eliminating certain foods temporarily.
Reoccurring stress of psychological factors - sometimes the mere thought of food can make you sick
Testing?
There are various IgG blood tests that you can get hold of now. The reliability of a lot of these test may not be great but they can be low cost and may be a starting point. Working with a Nutritional Therapist to understand the best test for you is a great idea.
There are much more relable and in-depth blood tests that you can do to understand an immune reaction to food. Cyrex laboritories offer such tests through a registered healthcare professional such as a Nutritional Therapist.
Please do get in contact for more information.
References
2016. Allergy And Immunology. 1st ed. [ebook] Melbourne: The Royal Children's Hospital Melbourne, pp.1-3. Available at: <https://www.rch.org.au/uploadedFiles/Main/Content/allergy/Non%20IgE%20Food%20Allergy.pdf> [Accessed 12 May 2020].
Allergy, Asthma and Sinus Specialists. 2000. The Process Of An Allergic Reaction - Allergy, Asthma And Sinus Specialists. [online] Available at: <https://www.cityallergy.com/13-the-process-of-an-allergic-reaction/> [Accessed 12 May 2020].
Allergyuk.org. 2020. Types Of Food Allergy | Information On Top 14 | Allergy UK. [online] Available at: <https://www.allergyuk.org/information-and-advice/conditions-and-symptoms/36-types-of-food-allergy> [Accessed 12 May 2020].
Anvari, S., Miller, J., Yeh, C. and Davis, C., 2018. IgE-Mediated Food Allergy. Clinical Reviews in Allergy & Immunology, 57(2), pp.244-260.
Connors, L., O’Keefe, A., Rosenfield, L. and Kim, H., 2018. Non-IgE-mediated food hypersensitivity. Allergy, Asthma & Clinical Immunology, 14(S2).
Gdx.net. 2020. Food Sensitivity Test | Igg Food Panel. [online] Available at: <https://www.gdx.net/uk/product/igg-food-antibodies-food-sensitivity-test-blood> [Accessed 13 May 2020].
Lavine, E., 2012. Blood testing for sensitivity, allergy or intolerance to food. Canadian Medical Association Journal, 184(6), pp.666-668.
Murch, S., 2004. MECHANISMS IN NON-IGE-MEDIATED FOOD ALLERGY AND THE ROLE OF IMMUNE TOLERANCE. Journal of Pediatric Gastroenterology and Nutrition, 39(Supplement 1), p.S550.
nhs.uk. 2020. Food Intolerance. [online] Available at: <https://www.nhs.uk/conditions/food-intolerance/> [Accessed 15 May 2020].
Ruffner, M. and Spergel, J., 2016. Non–IgE-mediated food allergy syndromes. Annals of Allergy, Asthma & Immunology, 117(5), pp.452-454.
Shakoor, Z., Al Faifi, A., Al Amro, B., Al Tawil, L. and Al Ohaly, R., 2016. Prevalence of IgG-mediated food intolerance among patients with allergic symptoms. Annals of Saudi Medicine, 36(6), pp.386-390.
Zopf, Y., Baenkler, H., Silbermann, A., Hahn, E. and Raithel, M., 2009. The Differential Diagnosis of Food Intolerance. Deutsches Aerzteblatt Online,.