What are food allergies and food intolerance?

What are food allergies

A food allergy is an abnormal reaction to a particular foodstuff (such as a seemingly harmless prawn, kiwi or piece of fish), which the body then considers as an intruder. The onset of a food allergy depends on individual genetic predispositions, the plants present in the environment and also on eating habits. Celery, for example, is more frequently consumed in Central Europe, resulting in a higher proportion of allergies there compared to the rest of the world.

An inherited family predisposition is called an atopy, i.e. a predisposition of the body to produce antibodies against substances in the environment. If either one of the parents is allergic, the child has a 30% chance of being so, while the risk is 70% if both parents are allergic.

Triggers and symptoms

Most triggers of an allergic reaction are plant or animal proteins, such as those found in chicken eggs, fish, bananas or celery. Walnut and peanut allergies are the most serious and, in rare cases, may even be fatal.

The most common symptoms of food allergies generally occur within two hours of ingesting the food and include swelling of the lips, eyelids, ears and tongue, abdominal cramps, a hoarse voice, tingling in the mouth or throat, eczema, dizziness, diarrhoea and vomiting. Symptoms can then affect all the organs, with digestive, skin, breathing or generalised manifestations and are, for the most part, irritating but harmless. In most cases, the first allergic reaction occurs during childhood or adolescence. If the symptoms are associated with a rash, swelling of the larynx, an asthma attack or anaphylactic shock (the most severe allergic reaction), it is recommended that the foodstuff having provoked them be avoided altogether.

Who is affected by food allergies?

Food allergies affect 5% to 8% of children, compared to 2% to 4% of adults. The most common allergies in children are to cow’s milk, chicken eggs and peanuts. In most cases, these allergies disappear during childhood. Many children also present allergies to walnuts, soya, fish and seafood, which tend to last into adulthood. Allergies present in adults include allergies to peanuts, walnuts, fish and seafood, as well as to apples, kiwis, peaches, celery, carrots and soya. The sudden onset of a food allergy is rare.

Food allergy or intolerance?

While around 20% of people questioned say they are allergic to a foodstuff, only 2% to 8% actually suffer from an allergy rather than an intolerance. One of the most common examples is gluten which is responsible, in Europe, for a real allergy in less than 1% of the population, while gluten intolerance affects 1% of the population.

According to the Swiss Federal Office of Public Health, more than one million people in Switzerland are affected by food intolerance. Unlike an allergy, food intolerance is not triggered by immunological mechanisms and does not require prior sensitisation. Allergies are characterised by a reaction to the ingestion of a tiny amount of food, while with an intolerance, the symptoms worsen as the amount ingested increases. The difference between suffering from an allergy or from a food intolerance lies in the severity of the reaction, as allergies are associated with much more severe consequences than intolerance.

It is worth noting that food poisoning is neither a form of allergy nor intolerance, but a normal response by the body to spoiled food.

How does an allergy work?

An allergy is a mechanism of the immune system which produces antibodies against what are usually harmless substances (called allergens). The allergic reaction does not occur with the first contact with the allergen, but with the second. The immune system becomes sensitive to the allergen during the first contact and is thereby ready to react when the body comes into contact with it a second time, even if it is a long time later.

Different types of food allergies

Wheat allergy

Wheat allergy, not to be confused with gluten intolerance, is due to proteins contained in wheat and is more common in children than in adults. The symptoms of this allergy revealed in adults generally appear immediately after ingesting wheat, but can also occur five to six hours later. Given that wheat is present in numerous food products, it is difficult to eliminate it totally from the diet.

Cow’s milk allergy

Cow’s milk allergy is due to the proteins contained in the milk. It generally appears very early in infants and disappears in 90% of children after the age of three. To treat this allergy, cow’s milk proteins should be eliminated from the diet, but, for the child’s development, it is vital to replace them by other sources of proteins such as plant proteins (soya or rice). For babies, Hypoallergenic substitute milk (HA milk) has been developed for babies. In HA milk, the proteins have been partially hydrolysed, i.e. they have been broken down into small pieces so that the immune system can no longer recognise them.

Egg allergy

Eggs, in particular certain proteins found in egg white, provoke allergic reactions more commonly seen in children than in adults. This allergy represents 30% of food allergies in children under fifteen but generally disappears around the age of four to seven. Egg allergy can, however, be permanent and accounts for 7% of food allergies in adults.

Peanut allergy

Peanut allergy is one of the most dangerous food allergies as it may have serious consequences., The incidence of peanut allergy is constantly on the rise and has doubled over the last ten years. Unfortunately, this allergy does not disappear as children grow into adulthood.

Soya allergy

Soya often provokes allergic reactions in children. However, in most cases, children outgrow this allergy by the time they are of school age.

Nut allergy

Nuts such as walnuts, hazelnuts, almonds and pistachios are common food allergens. In most cases, nut allergy persists throughout the person’s life. As with most food allergies, treatment essentially entails avoiding nuts. It is worth pointing out that a coconut is not considered a nut.

Fish and seafood allergy

Fish, crustaceans and molluscs are also responsible for food allergies which generally last throughout a person’s life. People who are allergic to fish are not necessarily allergic to seafood, and vice versa, but they are often allergic to several types of fish. As there is no treatment, the only solution is to avoid the allergen in question.

Sesame allergy

Sesame, a seed often found in Asian food and party snacks, contains proteins which can provoke an allergic reaction. This form of allergy continues into adulthood and avoiding sesame seeds is the only effective treatment.

Different types of food intolerance

Lactose intolerance

Lactase is an enzyme found in the intestine which breaks down lactose (a type of sugar found in milk) into glucose and galactose. While these two molecules are tolerated by most people, insufficient lactase (thus the inability to digest lactose) provokes the symptoms of lactose intolerance. Asians and Africans in particular only produce this enzyme in low quantities or not at all and most are therefore lactose intolerant. The majority of Europeans, however, generally tolerate medium amounts of lactose.

People who do not produce enough lactase or who have ingested too much lactose (after a fondue for example) suffer from nausea, abdominal cramps, flatulence and diarrhoea. This concerns 15% to 20% of the Swiss population.

Histamine intolerance

Histamine intolerance affects around 1% of the Swiss population. Histamine is a molecule which forms in products which ferment, mature or rot, such as processed meat, cured meat, mature cheese, wine, sparkling wine, beer and vinegar, as well as in strawberries, tomatoes and chocolate.

Disorders such as skin rashes, flatulence or diarrhoea have been observed and are due to a dysfunction of the enzyme diamine oxidase, involved in the breakdown of histamine. Chocolate, certain cheeses, processed meat, grapes and game also contain a substance called tyramine which can trigger similar reactions.

Gluten intolerance

Gluten is a component of various cereals (wheat, rye, oats) which can trigger a complex autoimmune reaction, meaning that the body directs the immune response against itself. This is referred to as coeliac disease. The symptoms in children are mainly developmental disorders and gastrointestinal conditions, while adults frequently suffer from anaemia or osteoporosis. The treatment of this disease involves the elimination of gluten from the diet.

Sulphite intolerance

Sulphites, found notably in white wine and champagne, are additives which can lead to headaches, nausea and asthma.

What is cross reactivity?

Does your tongue tingle after eating an apple and do you experience pollen allergy symptoms at the same time? It is not a sudden onset of an allergy to the apple, but a rare phenomenon called cross reactivity to a known allergen (pollen) when eating a foodstuff (an apple) whose proteins resemble those of this allergen. The immune system mistakes the proteins in the apple for pollen and triggers an allergic reaction resulting mainly in tingling and itchiness in the mouth, swelling of the tongue or a loss of feeling in the lips.

Different types of cross reactivity

Food allergies in adults and children over the age of five are generally associated with hay fever or other respiratory allergies for example to animal allergens (hair), latex or dust mites. It is estimated that 55% of people allergic to pollen (almost half a million people in Switzerland) develop cross reactivity to certain foodstuffs. These food allergies are thought to be caused by an allergy to pollen.

Among the most common forms of cross reactivity, some seem logical, such as the cross reactivity between the pollen of the hazelnut tree and hazelnuts, although others are less so, such as the cross reactivity between latex and kiwis or between dust mites and prawns. It is therefore a complex reaction which is very common yet difficult to determine.