Food allergy: everything you need to know about food allergies

Food allergy is an abnormal defense reaction of the body following the ingestion of food.

To find out all about allergies, see our sheet below.

Food allergy, what is it?

Food-triggered reactions can occur suddenly, within 2 hours of ingestion, or delayed, up to 48 hours later. This sheet only deals with immediate reactions caused by a food allergy. To find out more about gluten intolerance, food poisoning or food sensitivities, consult our sheets dedicated to these subjects.

Food allergy is an abnormal defense reaction of the body following the ingestion of food.

Often the symptoms are mild: tingling on the lips, itching or rashes. But for some people, the allergy can be very serious and even fatal. It is then necessary to banish the food or foods in question. In France, 50 to 80 people die each year as a result of a food allergy.

Food allergies usually appear before the age of 4 years. At this age, the digestive system as well as the immune system are not yet mature, which makes it more susceptible to allergies.

There is no curative treatment. The only solution is to ban the consumption of allergenic foods.

Note: Although it is rather rare, some people react strongly to the ingestion of various food additives. The reaction can be a real allergy if the additive, even if it does not contain protein, has been contaminated by another food containing it.For example, soy lecithin, which is non-allergenic, can be contaminated with soy protein. But most often, it is a food intolerance whose symptoms resemble those of an allergy.Additives like sulphites, tartrazine and salicylates can cause an anaphylactic reaction or an asthma attack. One in 100 asthmatics is sensitive to sulphites 2 .

The main allergenic foods

The most allergenic foods are not the same from one country to another. They vary in particular according to the type of food. For example, in Japan, rice allergy predominates, while in Scandinavian countries, it is more fish allergy. The following foods are responsible for about 90% of severe food allergies :

  • peanuts (peanuts);
  • shelled fruits (almonds, Brazil nuts, cashews, hazelnuts or filberts, macadamia nuts, pecans, pine nuts, pistachios, walnuts);
  • cow’s milk;
  • eggs ;
  • the fish ;
  • seafood (especially crab, lobster and shrimp);
  • soy le;
  • wheat (and related cereal varieties: kamut, spelled, triticale);
  • sesame seeds.
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Cow’s milk allergy is the one that occurs most frequently in infants, before the introduction of solid foods. This is the case for about 2.5% of newborns .

What is an allergic reaction:

When functioning properly, the immune system detects a virus, for example, and produces antibodies (immunoglobulins or Ig) to fight it. In the case of a person allergic to a food, the immune system reacts inappropriately: it attacks a food, believing that it is an aggressor to be eliminated.

This attack causes damage, and the effects on the body are multiple: itching, redness on the skin, production of mucus, etc. These reactions result from the release of several pro-inflammatory substances: histamine, prostaglandins and leukotrienes.

Note that the immune system does not react against all the components of a food, but only against one or a few substances. It is still a protein; it is impossible to be allergic to sugar or fat.

See our Animated diagram of an allergic reaction.

In theory, allergy symptoms appear at the time of the 2nd contact with the food. At the first contact with the allergenic food, the body, more specifically the immune system, becomes “sensitized”. At the next contact, he will be ready to react. The allergy therefore develops in 2 stages.

Click to see an allergic reaction in animation

Cross Allergies

These are allergies to substances that are chemically similar. Thus, a person allergic to cow’s milk is very likely to also be allergic to goat’s milk, because of the similarity of their proteins.

Some people who know they are allergic to a particular food prefer to refrain from consuming other foods of the same family for fear that they will trigger a serious reaction.

However, it is best to consult a doctor before making such a decision, as excluding foods can create deficiencies. Skin tests can detect cross allergies.

Here is an overview of the main cross allergies.

If allergic to:Possible reaction with:Risk assessment:
A legume (peanut is one of them)Another legume5%
PeanutA nut35%
A nutanother nut37% to 50%
A fishanother fish50%
a cerealanother cereal20%
A seafoodanother seafood75%
Cow’s milkBeef5% to 10%
Cow’s milkGoat’s milk92%
Latex (gloves, for example)Kiwi, banana, avocado35%
Kiwi, banana, avocadoLatex (gloves, for example)11%

Source: Quebec Food Allergy Association

It happens that people allergic to pollen are also allergic to fresh fruits or vegetables, or to nuts. This is called oral allergy syndrome. For example, a person with a birch pollen allergy might have itchy lips, tongue, palate, and throat when eating a raw apple or carrot.

Sometimes swelling of the lips, tongue and uvula, as well as a feeling of tightness in the throat may occur. The symptoms of this syndrome are usually mild and the risk of anaphylaxis is low. This reaction occurs only with raw products since cooking destroys the allergen by modifying the structure of the protein.

Oral allergy syndrome is a form of cross allergy.

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