Food allergy sufferers and those with a food tolerance alike can quite easily be picked out from the crowd by the way they stalk supermarket aisles, studying ingredient lists. As we know, an allergy to food can, in the worst-case scenario, be deadly. When we talk about food intolerances, we instead talk about symptoms that range from discomfort to acute pain, rather than a life-threatening condition.
Concerned individuals must change their diets and steer clear of possible food triggers to avoid any nasty surprises after dinner that can range from stomach rumbling, severe flatulence, rashes and dizziness to anaphylactic shock. And it is not always easy to identify a specific foodstuff allergy with the symptoms. The real challenge in many cases is to find out exactly what it is that you cannot tolerate. We can tell you how to do that.
So, to help you out, we have broken down the differences between a food allergy and a food intolerance, giving you some pointers on how you might be able to discover which of the two affects you. Find out which steps to take to improve your everyday health and well-being, such as an elimination diet or taking a self-test.
What is a food allergy?
When you have an allergy, your immune system reacts strongly to an otherwise harmless substance. The substances which can trigger allergies are known as allergens. These different proteins may be present in pollen, animal hair, the faeces of dust mites or even in food.
What is an allergen?
An allergy always starts with a sensitisation towards an allergen. This means that the body will produce certain IgE antibodies in an excessive amount. Each of these immunoglobulins (the ‘Ig’) specialises in keeping specific intruders out of the body. In doing so, the immune system will combat bacteria, viruses and worms – but unfortunately, also harmless allergens.
IgE antibodies bind to receptors on mast cells, which are cells of the immune system. Laboratories can detect the increased number of IgE antibodies in the blood and assign these to their corresponding allergens – and this is how an allergy test by blood sampling works. If the allergen is present in the body again, the allergen will bind to the IgE antibodies and cause the mast cell to release messenger substances, such as histamine. Histamine then promotes inflammation and, in so doing, triggers the different symptoms of an allergy.[5, 6]
What types of food allergies are there?
Experts distinguish between different types of allergy. The most common forms of allergy are those of the immediate type – namely, type I allergies, which also includes food allergies. The reaction occurs directly after you have consumed the allergen. A person allergic to peanuts feels symptoms such as a furry tongue and rash between a few seconds to around 20 minutes after eating. Delayed immediate reactions are also possible, meaning an allergic reaction can occur after four to six hours.
Some food allergies can resolve themselves during adulthood. For example, milk, egg, soy and wheat allergies usually affect children and then disappear in 90 per cent of cases. Allergies to nuts, fish and shellfish, however, are usually there to stay.
What causes a food allergy to develop?
Allergies are today talked of as a disease of modern civilisation. The number of allergies has increased steadily over recent decades. Scientists are not quite sure why this has been the case. A popular explanation is the hygiene hypothesis, which has blamed the frequency of allergies today on our tendency to avoid dirt and germs. Nevertheless, genetic factors also seem to play a role.
Are allergies inherited?
Is there a connection between allergies and human genetics? As a rule, nobody is born with an allergy. But humans can have an inherited predisposition when it comes to developing an allergy. In other words, you can have a significantly higher risk of developing an allergy. This often applies to allergies in general – that is, the children of parents with hay fever are susceptible to all allergies, whether it be to pollen, animal hair or food. This also applies to other topical or contact diseases, which are closely related to allergies and which often occur together with them (such as with atopic dermatitis and asthma).[10, 8, 11]
For an unborn baby, the womb is their home, and this influences how its body develops. As such, a mother’s diet can also influence the development of allergies. Giving birth by caesarean section and at a high age also seem to increase the risk of developing a food allergy.
What is the hygiene hypothesis?
The hygiene hypothesis is based on the observation that allergies are particularly prevalent in cities and much less common among children raised on a farm. The theory goes that in the hygienic environments we inhabit in the Western world, our immune system seldom encounters foreign bodies, such as pathogens, worms and parasites. Our bodies’ defences have comparatively little to do and only rarely put into action to defend themselves against harmless substances such as food and pollen – and this is how an allergy arises.[10, 9, 12]
Whether we develop an allergy over the course of our lives is decided during the first months of us being alive – and perhaps even in the womb. It therefore depends on the environment in which babies live at the beginning of their lives.
Does gut health affect allergies?
The microbiome (also known as the intestinal flora) describes the composition of the billions of bacteria that inhabit our gut. This microbiome plays a key role in helping our immune system develop from early childhood onwards. Researchers suggest that our modern way of life affects intestinal bacteria, which, in turn, can have an impact on the development of allergies.
A study from Estonia showed that Estonian children, who still grow up relatively frequently on farms and spend a lot of time outdoors, have a much better bacterial colonisation of their intestines than children from Sweden, who are less likely to grow up on farms.
Is there a link between breastfeeding and food allergies?
For the immune system to develop healthily, mothers should ideally breastfeed their infants for at least four months. Until just a few years ago, strict nutritional guidelines were recommended. To reduce the risk of allergies, breastfeeding women had to avoid eggs, nuts, dairy products and wheat products. Experts also advised against contaminating baby porridge with gluten-containing grains. And fish was just as much taboo, as were celery and carrots.
New studies have turned these recommendations on their head. They show that children are more likely to tolerate foods if they have been in contact with them while still in the womb or feeding on breast milk. Of course, this only applies if the child has not already developed an allergy!
How to prevent allergies
The emergence of an allergy is a complex process that scientists still do not fully understand. There are thus no official recommendations on allergy prevention.
Medical guidelines, however, provide recommendations that make an allergy a little less likely. They are aimed at ‘at-risk families’ – that is, at families in which allergies, atopic dermatitis or asthma also occur. Recommendations furthermore include:
- The mother and child should not refrain from consuming allergens as part of the diet, since even the consumption of fish by the mother can protect against allergies.
- During pregnancy, mothers should avoid tobacco smoke.
- Children and pregnant or breastfeeding women should not come into contact with mould.
- Cats should not be kept as pets – unless the child is at a high risk of developing a cat allergy. In this case, exposure to cats can actually have a positive effect.
- There should be as minimal exposure to vehicle exhaust as possible.
What are the most common food allergies?
There are a total of 170 foods that are allergens, but most reactions are triggered by just a few culprits. The most common allergens are cow’s milk, eggs, peanuts, nuts, soy, wheat, fish and shellfish.[17, 18]
Cow’s milk allergy
A cow’s milk allergy is the most common food allergy. It usually manifests during childhood before it disappears again in later childhood. Those who suffer from this particular allergy react to all dairy products, including cheese, yogurt, butter and cream – and 92 per cent are also allergic to goat’s milk. People with a cow’s milk allergy should also avoid goat and sheep’s milk products.
Please note: An allergy to cow’s milk is completely different from lactose intolerance.
Chicken egg allergy
A chicken egg allergy is the second most common food allergy to develop during childhood after a cow’s milk allergy. It very often resolves itself in adulthood.
Some foods do not trigger as strong an allergic reaction when they are cooked. For example, many people with allergies can much better tolerate adequately cooked milk or eggs used in baking. When roasting peanuts, on the other hand, there is an even greater chance of triggering an allergic reaction.[22–24]
With a nut allergy, doctors distinguish between allergies to peanuts – which are actually legumes – and other nuts that they refer to as tree nuts. All nut allergies tend to trigger relatively violent reactions that even extend to anaphylactic shock.[25, 26]
Fish and shellfish allergy
A fish allergy is often only seen in adulthood. Affected people usually cannot tolerate any sort of fish. Most individuals allergic to fish, however, can easily eat shellfish and vice versa.
A shellfish allergy also usually develops during adulthood. Shellfish include all crustaceans, including crabs and lobsters, molluscs, oysters, scallops and squid – as well as insects such as cockroaches and locusts. Since house dust mites are crustaceans, shellfish allergy sufferers also often respond to house dust.
Wheat allergy most commonly emerges during childhood and usually disappears before adulthood. A total of 20 per cent of people allergic to wheat experience cross-reactions with other cereals, such as spelt or rye. But you should not eliminate all cereals from your meals, as this would restrict your diet too much. If in doubt, take an allergy test. It’s far better to do this and identify what you can and can’t tolerate with a provocation test, for example.
Please note: A wheat allergy is not coeliac disease! Wheat allergy sufferers can still consume foods containing gluten, as long as they do not contain wheat.
Now, we get to a lesser-known allergy: a spice allergy. Spices are found in all sorts of processed foods, cosmetics and dental products. However, they do not have to be labelled on the packaging. This makes it difficult for allergy sufferers to avoid certain spices. However, spice allergies are relatively rare. The most common spice allergies are to cinnamon and garlic – but allergic reactions may also occur with black pepper and vanilla.
Cross-reactivity: what does cross-allergy mean?
It is not the foodstuff itself that triggers an allergic reaction, but rather certain proteins within them that act as allergens. Sometimes, different types of these proteins are so similar that the body can not tell them apart. In such a case, a cross-reaction may occur. This is when the body is sensitised towards one allergen but also reacts to the other. This happens with foods – for example, those allergic to peaches often are allergic to apples. In addition, a pollen allergy sometimes leads to a cross-reaction with fruits, vegetables and nuts. Surprisingly, even latex often triggers cross-allergies – to kiwis, bananas and avocados.
Foods and their potential cross-allergies:
Risk of cross-allergies
92 per cent
Watermelons, bananas, avocados
92 per cent
75 per cent
Apples, plums, cherries, pears
55 per cent
Apples, peaches, honey melons
55 per cent
50 per cent
Brazil nuts, cashews, hazelnuts
37 per cent
Kiwis, bananas, avocados
35 per cent
20 per cent
Food allergy symptoms
A variety of symptoms may indicate the presence of an allergy or intolerance. Some are mild and barely noticeable, while some cannot be overlooked – and others are even very severe, with symptoms such as an anaphylactic shock. Food allergies do not always just affect the mouth and gastrointestinal tract; they also impact the skin and respiratory tract.[10, 7]
What are the signs of a food allergy?
During an allergic reaction, the following symptoms frequently occur:
- Redness and wheals on the skin (nettle fever)
- Diarrhoea, vomiting and abdominal pain
- A burning sensation in the oral cavity, swelling of the mucous membranes and tongue
- Breathlessness or allergic asthma
- A fall in blood pressure
Anaphylaxis: the worst-case scenario
The most severe form of an allergic reaction is an allergic shock, which is also referred to as an anaphylactic shock. The causes of this are usually insecticides, medicines and, especially in children, food. But foods such as nuts, soy, shellfish, milk and eggs can also cause anaphylaxis.
During an anaphylactic shock, large amounts of histamine are released, resulting in severe dilation of the blood vessels. Blood pressure falls rapidly, while dizziness, fainting and even death can occur in the worst-case scenario.
If you are aware that you are at risk of having an anaphylactic shock, you should respond quickly if more severe allergic symptoms occur and call the emergency services immediately. While waiting for the ambulance to arrive, the individual in shock should be placed in the shock position – that is, lying down with their legs up. At-risk patients also often carry an emergency kit containing an adrenaline pen. This emergency medicine will ensure that the shock subsides.[5, 6]
Depending on the severity of an allergy, even the smallest amounts of an allergen can trigger an anaphylactic shock – such as traces of nuts on your partner’s lips or traces of soy in certain foods.[5, 6]
Factors that exaggerate an allergic reaction
Just because you have an allergy, this doesn’t mean you will automatically respond to the smallest amount of the allergen. A reaction threshold exists, meaning that you need exposure to a certain amount of the allergen before symptoms occur. As an example, peanut allergy sufferers often have a very low reaction threshold, with a small crumb of a peanut being enough to lead to a furry tongue and swollen neck.
Stress, sports and infections can also lower your reaction threshold. This will make you more likely to suffer from an allergic reaction.
During or immediately after exercise, the risk of an allergic reaction is increased. This phenomenon even has a name: namely exercise-induced anaphylaxis (EIA). If you eat a food that you are allergic to right before exercise, you may experience hives and itching, or feel drowsy. You should avoid any of your food allergens at least four to five hours before each workout.
Studies have shown that stress can make the symptoms of allergy worse and more likely to occur. If you suffer from an allergy and are often stressed out, seek out relaxation techniques, such as yoga, training and progressive muscular relaxation.
Infections can also set off allergies. An elevated temperature can namely lead to increased blood circulation, which, in turn, can allow more allergens to enter the bloodstream. With infections in the gastrointestinal tract, allergies are aggravated by a larger quantity of undigested proteins crossing the mucous membrane. As a result, such proteins affect the sensitised immune system and are more likely to trigger an allergic reaction.
Alcohol is also discussed among scientists as a factor exaggerating allergic reactions. In some case studies, allergy symptoms were exacerbated under the influence of alcohol, and for alcoholics, the number of IgE antibodies is often greater. Conclusive scientific evidence for this correlation, however, does not yet exist.
How is food allergy testing done?
Do you suspect that you cannot tolerate certain foods due to subsequent symptoms such as a rash, furry tongue or gastrointestinal discomfort? Then it may be worthwhile for you to take a food allergy test. There are a handful of common tests that can detect allergies:
- prick test
- blood test for IgE antibodies
- hair test
- elimination diet
- oral provocation test
The prick and blood tests provide evidence of merely a sensitisation towards certain allergens. Elimination diets and provocation tests serve to find out whether an allergy is behind the sensitisation.
Treating a food allergy
Food allergies can not be treated as such. Once you have them, you have to live with them, unless they resolve themselves. However, based on a reliable diagnosis, you can avoid the triggers, relieve discomfort with medications and arm yourself with an emergency kit to treat anaphylaxis.
Avoid triggers and eat a balanced diet
This much is clear – if you have a food allergy, you should stop consuming that food, even in small quantities. If your allergy is accompanied by severe discomfort or even the risk of anaphylactic shock, you should carefully study the ingredients on food packaging. Heavily processed foods, in particular, often contain ingredients that you would not necessarily expect.
An EU regulation requires food manufacturers to clearly label the 14 most common triggers of allergies and intolerances on their products: gluten-containing cereals, crustaceans, eggs, fish, peanuts, soybeans, dairy products, nuts, celery, mustard, sesame seeds, sulphur dioxide and sulphites, lupins, molluscs. The term ‘May contain traces’ is not regulated, with manufacturers using it voluntarily.
If you only have reactions to one or two foods, it is often easy to eliminate them from your diet and replace them – especially in today’s world, where there has been a noticeable boom in the food replacement industry. However, if you or your family have a lot of food allergies, cooking meals can become quite a mission. Experts recommend dietary or nutritional advice in such cases. You will then learn how to avoid allergens while still maintaining a balanced diet.
Antihistamine for allergies
Antihistamines, which are also known as anti-allergic tablets, weaken or even block the messenger histamine. In this way, they can combat allergic reactions throughout the body. Such tablets are used for hay fever, but can also relieve minor food allergy symptoms, such as rashes, palatal itching or nausea. The most common active ingredients are cetirizine and loratadine, and these are available as drops or tablets over the counter in many pharmacies.
With an anaphylactic shock, however, the effect of antihistamines is usually not sufficient. That is why people with severe allergies to more dangerous allergens, such as nuts and shellfish, often carry an emergency kit with them. The emergency kit includes an adrenaline pen which is injected into the thigh, glucocorticoids and, for asthma sufferers, an inhalation spray.
What is a food intolerance?
Did you know that symptoms of an intolerance can also originate in the psyche? For example, your brain may associate traumatic memories with a certain kind of food. Sometimes the body will then react with discomfort when you consume the food again.
What are the signs of a food intolerance?
Intolerances are usually delayed, unlike allergies. If you eat something that you can not tolerate, it can take hours for symptoms to manifest. This often makes it difficult to detect an intolerance and to find out what food is responsible for it.
The symptoms of intolerance are usually noticeable in the gastrointestinal tract. Unpleasant flatulence is typical, but it can also lead to nausea, constipation, diarrhoea and vomiting. Other possible symptoms include:
- Headaches and migraine
- Whistling breath sounds and a runny nose
Tip: If you’re not sure about where to start when it comes to food intolerance testing, you can keep a food diary to keep track of your meals and when you experience symptoms, as well as which symptoms you experience. This will undoubtedly help you narrow down the foods you could be intolerant to before you take every food intolerance test under the sun.
What are the 3 most common food intolerances?
Scientists today already more or less understand a number of intolerances. We tend to know roughly what’s going on in our guts and why sufferers can no longer tolerate certain foods. Well-researched intolerances include lactose, histamine and coeliac disease, fructose and sorbitol.
1. Lactose intolerance
Chances are, you have already heard of a lactose intolerance. Lactose is a sugar found in milk and many dairy products. In Ireland, lactose intolerance affects up to four per cent of the population. In other regions, especially in East Asia, it is even more common: in fact, it has been reported that between 70 and 100 per cent of adults are affected by lactose intolerance in these regions.
In affected individuals, the specific enzyme that breaks down lactose occurs at low levels in the intestine. The body can not process the lactose properly, leading to flatulence and abdominal pain.
Did you know that humans started consuming milk from domesticated animals long before the Bronze and Iron Ages? This is why Eurasians are able to better tolerate lactose than other citizens around the world.
2. Gluten intolerance (coeliac disease)
With coeliac disease, the protein gluten triggers an immune reaction that leads to inflammation in the intestinal mucosa and subsequent gastrointestinal discomfort – and long-term to nutrient deficiency and consequential symptoms, such as osteoporosis and anaemia. Gluten is found in many cereals – for example, in wheat, spelt and rye, as well as in many processed foods. This can therefore be frustrating for anyone with a gluten intolerance.
3. Histamine intolerance
A histamine intolerance is also referred to as a pseudoallergy. Like a food allergy, histamine levels lead to symptoms such as redness, flatulence, dizziness and a runny nose. But while immune cells release too much histamine during an allergic reaction, a histamine intolerance is caused by a lack of a specific enzyme in the gut and blood that breaks down histamine in food. Histamine-rich foods such as red wine, mature cheeses and dried sausage can then trigger its symptoms.
Curious to find out more? Click here to read our article on histamine intolerance!
In addition to IgE antibodies, the immune system has other defence mechanisms, including IgG4 antibodies, or immunoglobulin G4. Our body also produces different IgG4 antibodies in response to all kinds of foods that we consume.
What does an IgG4 test tell you?
According to theories, the production of certain IgG4 antibodies increases all the more when we cannot tolerate a certain food, leading to various defence and inflammatory reactions. This leads to an IgG4-mediated intolerance. These reactions and the associated symptoms only occur after a delay, and sometimes only hours or days after the food was eaten. The number of IgG4 antibodies can be determined using a blood test, and also using the cerascreen® Food Reaction Test. The result might then be a sign of an intolerance.
Some researchers and professional societies have criticised that the IgG4 concentration only provides information on the extent to which certain foods were eaten and that it is not clinically relevant. It instead points towards an immune tolerance rather than an intolerance. Thus far, there has been no large-scale study investigating the link between IgG4 levels and food reactions.[1, 4, 35]
Intolerance to histamine, lactose, fructose and sorbitol as well as coeliac disease cannot be detected using an IgG4 intolerance test. In each case, other blood or respired gas tests are required.
How can I interpret my IgG4 test results?
An increased number of IgG4 antibodies does not mean that you cannot tolerate a food. However, you can still deliberately omit the foods identified in the test from your diet and check whether your symptoms start improving. If the test shows a clear reaction to a food, remove it from your diet for two weeks. If your symptoms improve, then this is an indication that an intolerance might be present. You can then forgo that food for the next six months. Only then try to reintroduce it back into your diet slowly.
An alternative would be a rotation diet. With this diet, you can omit several potential intolerance triggers. To do this, eat the foods you responded to in the IgG4 test only every four days. This will allow your intestines to recover in the meantime. Such a rotation can already lead to a significant decrease in discomfort.
Food reactions – at a glance
Food allergy versus food intolerance
A food allergy, as it is defined, is always a reaction of the immune system in which specific antibodies play a role, usually the IgE antibodies. This must be differentiated from food intolerance that causes non-immunological reactions to food. Instead of incompatibility, the term intolerance is often used.
What is a food allergy?
With a food allergy, our immune system tries to combat usually harmless proteins called allergens that are found in foods. The mast cells of our immune system release histamine, and this causes inflammation that can bring about discomfort in the whole body.
What are the symptoms of a food allergy?
A food allergy can manifest itself through gastrointestinal discomfort, palatal itching and a furry tongue. However, reddening, itching and rashes on the skin as well as respiratory complaints and even asthma are also common. In rare cases, a fall in blood pressure and an anaphylactic shock might occur.
Which foods can trigger an allergy?
Theoretically, many foods can trigger allergies. In practice, however, just a few foods are responsible for more than 90 per cent of all allergies. These include cow’s milk, eggs, peanuts, nuts, soy, wheat, fish and shellfish.
How can I recognise a food allergy?
If a food allergy is suspected, one of the things you can do is take a blood test. The test determines the numbers of certain IgE antibodies in your blood. If an IgE level is elevated, a sensitisation towards the antibody-related food exists. Then you can avoid the food temporarily to see if your symptoms are alleviated.
What is a food intolerance?
In the case of an intolerance, symptoms do not arise through immune reactions as they do with an allergy. Often, the gut has problems processing certain ingredients of foods, such as gluten, histamine, lactose or fructose.
What are the symptoms of food intolerance?
In contrast to a food allergy, intolerance symptoms are often not immediate. Sometimes symptoms only appear after hours or days. Typical symptoms include gastrointestinal complaints, and particularly flatulence, headaches and migraines, runny nose, rashes and fatigue.
What is an IgG4-mediated food intolerance?
The IgG4 antibodies of the immune system can, according to some theories, provide an indication of intolerance towards a food. Using the IgG4 values measured in a blood sample, you can embark on elimination and rotation diets that might help prevent more intolerances and reduce discomfort.
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