Most of the functions and cells in our body are made up of proteins, otherwise known as amino acids. These amino acid chains come in many forms of foods. A food allergy occurs when we have an immune response to certain proteins in foods. You might wonder why a vegetable, fruit, or wheat might trigger allergy when they are not a source of protein themselves. This is because even plant foods contain glycoproteins, a type of protein that still has an influence on the body.
When it comes to food allergies proteins can enter via skin, digestive tract, or airways. Food intolerance is slightly different in that it is when we have a more moderate hypersensitive immune response. There is an important difference as food allergy can literally kill a person (such as in anaphylaxis), whereas food intolerance may cause a lot of discomfort but it won’t kill you.
Food allergens can also be found in medications, vaccines, cosmetics, children’s crafts, or in the body fluid of others. So people with known allergies have to be particularly careful. People can be allergic to one food or sometimes have multiple allergies.
The thing is 20-30% of people who think they might have a food allergy really only have a food intolerance. Many of the food sources that cause allergies also cause intolerances so it can get a little confusing. But let’s dig into the whole concept of food allergy to understand some of the common causes and symptoms. We’ll also explore the different types of food allergies, and why children are more prone to food allergies than adults.
Class 1 Food Allergens
These types of food allergens are known as primary sensitizers, meaning most people prone to allergies will primarily react to these foods.
|Food||Allergy causing component (proteins)|
|Cow’s milk||Caseins (a,b,k) a-lactoalbumin, B-lactoglobulin|
|Chicken egg||Ovomucoid, ovalbumin, ovotransferrin|
|Peanuts||Vicillin, conglutin, glycinin|
|Soybeans||Glycinin, progilin, trypsin inhibitor|
Cross Reactive Foods
People with allergies may also react to foods within the same family.
|Index Allergen||Risk of Cross reaction||Percentage risk|
|Peanuts (aka a legume)||
<-Sensitive to these?
You may also
with these ->
|Other legumes = beans, lentils, peas||5%|
|Wheat (aka grain)||Other grains = rye and barley and more rarely other grains also||25%|
|Walnuts (aka tree nut)||Other tree nuts = brazil, cashew, hazelnut||15-40%|
|Salmon (aka fish)||Other fish = sole, swordfish||50%|
|Shrimp (aka shellfish)||Other shellfish = crab, lobster||75%|
|Adapted from source: (1)|
Food allergies are increasing in industrialised countries
Why is this occurring?
Researchers don’t fully understand it but the general theory is that this increase is due to increased exposure to environmental toxins, overexposure to processed foods, additives and chemicals in foods, and a condition known as leaky gut, which is increasing in prevalence. This is when the digestive system is compromised and proteins can re-enter the bloodstream.
Main food allergens in adults
The main food allergens in adults in many developed countries are:
- tree nuts
- and shellfish
Risk Factors for developing food allergies
The most predictive risk factor for development of food allergy is family history of allergic diseases such as:
- hay fever
Children and food allergies
The most common food allergies in children include:
- tree nuts
Basically many of the class 1 allergens are more prominent in children.
Milk and egg allergies are usually outgrown, whereas other allergies might persist into adulthood.
Why do children get more food allergies?
Children more commonly get food allergies because their digestive tract is not fully developed. There are tight junctions between the mucosal cells in our digestive tract that haven’t yet closed tightly in children. This means that many children have what’s known as leaky gut. This is where undigested proteins can cross the gut barrier more easily, entering the bloodstream and activating an immune response.
Once these tight junctions close and the digestive tract is more developed, allergies and food intolerances in children often disappear. To avoid long-term allergies, allergy specialists and researchers now recommend that small amounts of allergy forming foods should be introduced from 6 months of age, rather than avoiding them all together because this helps build immunity. That is of course only if your child does not have a severe allergy where anaphylaxis is caused. This only occurs in a small number of people but is something to be aware of as it can cause death (more info below).
Common symptoms of food allergy in children include:
Manifestations of various forms of food allergies
There are 3 types of food allergy: IgE mediated, mixed (IgE/Non-IgE), and non-IgE mediated. If you suffer with a food allergy, you’ve probably heard of these. If not then you’ll probably learn something about them now.
The following picture shows the different immune responses to the different types of food allergy.
A person may experience a rapid onset reaction followed by a delayed onset reaction, or they might just experience one of the immune response pathways.
IgE-mediated reactions are rapid in onset and are considered to be acute reactions. They can also develop into chronic issues. IgE-mediated allergies can effect multiple systems in the body such as the skin, airways, mouth, eyes, ears, gastrointestinal tract, and cardiovascular system.
Oral allergy syndrome
This is a common but mild form of food allergy that occurs from fruits, vegetables or as a reaction to pollens. Symptoms are usually limited to the mouth and include:
- red bumps like hives but under the skin
- swelling of the lip, oral mucosa, palate, and throat
These symptoms will occur during or soon after contact with the allergen. Many children will out grow these types of allergies; other people may just have to avoid certain things if symptoms persist. 1 in 10 may experience anaphylaxis.
We’ve probably all heard of anaphylaxis in regard to peanuts because this is one of the most common cause of anaphylaxis. Other common severe allergic reactions and anaphylaxis include other nuts, seafood, milk and eggs. However anaphylaxis can actually occur with any food. Anaphylaxis has an incredibly rapid onset of symptoms and usually involves multi-organ system that can be potentially fatal. People with known allergies that trigger anaphylaxis often carry epipens, which are an adrenaline shot to assist the cardiovascular system to keep operating until they can get medical attention. These have been a real life saver.
Non-IgE mediated food allergy (cellular, delayed type)
Non-IgE mediated food allergies are slower acting in effect than IgE-mediated allergies. They can also be chronic in nature but generally most non-IgE mediated food allergies are associated with isolated gastrointestinal symptoms, so symptoms around your digestion.
Symptoms such as:
- inflammation of digestive tract
- inflammation of the bowel or rectum
- celiac disease
- contact dermatitis
- itchy rash or bumps with blisters
- Gastrointestinal symptoms such as – bloody stolls. malabsorption, weight loss, consitpation, and failure to thrive.
Food Protein-Induced Enterocolitis Syndrome (FPRIES)
This condition is not frequently recognised and also frequently gets mis-diagnosed. It occurs in babies 8-12 months of age due to cows milk and soy formulas.
- protracted vomiting 1–3 h after feeding
- bloody diarrhea
- abdominal distension
- and failure to thrive
In adults and older children, fish, shellfish, and cereal hypersensitivity may provoke a similar syndrome with delayed onset of severe nausea, abdominal cramps, and protracted vomiting.
Food Protein-Induced Enteropathy (Excluding Celiac Disease)
This occurs in infants from 0-24 month olds . The symptoms include chronic daiarrhea, malabsorption, and failure to thrive. Most common food causes are milk, cereals, eggs, and fish. If there is an allergy to these foods it can also be passed to infant via breast milk or from cow or soy based formula. Definitive diagnosis requires a mucosal biopsy but people respond well to an elimination diet of problematic foods. A great place to start with any elimination is milk and eggs as these are the most common source of issues. If you exclude the food and symptoms subside, then re-introduce the food, a fast relapse of symptoms will occur on reintroduction and you will identify your problem food.
Mixed IgE/Non-IgE Mediated food allergy
A mixed allergy response produces the following symptoms:
- Atopic Eczema that commonly begins in childhood. 90% of children with this issues have allergy to milk, egg and/or peanut.
- Allergic Eosinophilic Disorders occurs in both children and adults and result in gastrointestinal issues.
- Allergic eosinophilic esophagitis (AEE)
- Reflux – mostly in children
- Dysphagia and impaction in adults
- Allergic Eosinophilic Gastroenteritis (AEG) – results in vomiting and diarrhea after meals and can be associated with occult blood loss that results in iron deficiency.
If you’ve tried medication for reflux and it hasn’t worked then you may very well have a food allergy as most people with AEE will not respond to the medication. People with AEE also frequently have skin complaints, dryness, itchiness and so forth.
As you can see there are a wide array of different food allergies, along with symptoms. The point being that if you have issues that are unresolved by other means, don’t exclude food allergies as a possible problem delaying your recovery.
So how can you know?
Food allergy testing
You can get food specific IgE testing. Lab testing is also available for some of the types of symptoms outlined above. However, majority of food allergy testing is still dependent on elimination diets and challenge testing.
As already mentioned above, a great place to start with any elimination is milk and eggs as these are the most common source of issues. If you exclude the food and symptoms subside, then re-introduce the food, a fast relapse of symptoms will occur on reintroduction and you will identify your problem food. You can try this with any food you suspect as being a problem, or you could ask your doctor for food specific allergy testing.
Food additives in relation to food allergies
Food additives, which are ample in our modern food supply, have not been well studied for their potential health impacts. Although most are considered ‘safe’, the safety aspect is usually given the approval in regard to that singular additive only. The relationship of many food additives combined together and causing food allergies is a vastly under studied area, this is a sad fact but true!
Food additives additives come in the form of colourings, preservatives, sweeteners, thickeners, antioxidants, and the list goes on. I’m sure you’ve seen the vast list of numbers on some packaging.
Being that food additives are so ample in our modern food supply it would not be surprising to me that these could cause allergic effects, much more than researchers are currently aware of. Like I said, food additives are vastly under studied. As you can imagine we do have large food companies with a directive against researching food additives. Or at least you wouldn’t get too many of them funding research, right?
Known food additive reactions
Note: research on these is still minimal.
MSG (No:621) (aka Chinese restaurant syndrome) – symptoms include nausea, myalgia, neck pain, backache, sweating, flushing, and chest tightness.
Artificial coloring or a sodium benzoate (No:210) preservative – a randomized control trial (strongest form of study) showed that children experience increased hyperactivity. (2)
Tartrazine (No:102) – symtpoms include hives, diarrhoea, other digestive disorders, and asthma. (2)
Got allergy tests and it shows nothing?? It’s probably not your imagination
Although many medical practitioners and researchers deny the physical symptoms if there is no solid evidence, a study done by Dr Genius (love the name) showed that 3-4% of the general population has food allergy due to multiple chemical sensitivity. (3)
What is multiple chemical sensitivity? (MCS)
In our modern world we are exposed to hundreds of chemicals that are highly unnatural to our natural biological being. When we are exposed to these chemicals the effects don’t disappear but research shows we are left with a toxic burden. 10. Ongoing chemical exposure around us does have the potential to induce an immune response. Essentially the immune system becomes hypersensitive. It certainly doesn’t happen in everyone but it does happen.
The picture below (source-3) explains how this process might occur.
Low dose exposure to chemicals over time leads to a low grade inflammatory response that can begin the recruitment of cytokines (inflammatory cells). This can trigger the inflammatory cascade and dysregulate the immune system, therefore you can end up with allergies or possibly other health issues.
MCS can present as a food allergy or an intolerance to foods, molds, inhalants, or chemcials.
|Mild symptoms of chemical sensitivity||Major symptoms of chemical sensitivity|