Symptoms, risks, treatments… how to prevent food allergies and who children are at risk ?

Allergies alimentaires :  qui sont les enfants à risque ?

Lait, œuf, arachide, fruits à coque, poisson, mollusques et crustacés sont les aliments les plus fréquemment impliqués dans les allergies alimentaires chez les enfants.

Constantly increasing, these concern nearly 6% of those under 15, compared to 2% 20 years ago*. How to explain this increase in food allergies ? Can we prevent them ? On the occasion of World Allergy Week, from June 24 to 29, we take stock with Guillaume Lezmi, pediatrician allergist at the Necker-Enfants Malades hospital (Paris).

What is a food allergy ?

Dr. Guillaume Lezmi: Food allergies are hypersensitivity reactions to foods, caused by immunological mechanisms. We distinguish between immediate allergies and delayed allergies. Immediate allergies occur within 2 hours of consuming the food. They are caused by allergenic antibodies called IgE, developed against foods (we speak of IgE-mediated allergies). Delayed allergies occur within hours of contact with the allergen. They are not caused by IgE and are responsible for variable chronic symptoms such as transit disorders (for example chronic diarrhea), growth retardation, bloating, etc.

What are the symptoms of immediate allergies ?

The most common symptoms are mucocutaneous damage such as hives, edema (swelling), pruritus (scratching sensation), allergic rhinoconjunctivitis. Symptoms can be severe or even fatal in cases of anaphylaxis, with respiratory distress due to bronchospasm or laryngeal edema (angioedema), malaise, anaphylactic shock.

What should you do in the event of allergic signs after exposure to a food ?

Mild mucocutaneous reactions are treated with oral antihistamines. On the other hand, the most severe reactions require one, rarely several, intramuscular adrenaline injections and urgent medical attention. After the reaction, you must of course stop all consumption of the suspect food and consult a specialist. The allergist confirms the diagnosis based on the patient's clinical history and the demonstration of antibodies directed against the suspected allergen using skin tests (prick tests), or the dosage of specific antibodies in the blood. Non-IgE-mediated allergies (mainly to milk or wheat) are sometimes more difficult to diagnose because their manifestations are non-specific and there are no reliable tests to diagnose them.

What are the risk factors for the occurrence of a food allergy in children ?

severe atopic dermatitis. About 20 to 30% of children with severe atopic dermatitis have food allergies. There is probably also a slight increased risk in children of allergic parents.

Can we prevent the occurrence of food allergies in children ?

It is now shown that early consumption during diversification, from the age of 4-5 months, of peanuts, nuts and eggs prevents ;rsquo;allergy to these foods. These recommendations apply to children most at risk (with severe atopic dermatitis) but also to the general population, because certain children without any risk factors can develop an allergy.

Why are food allergies on the rise in recent years ?

We don't know exactly, but several avenues have been put forward. The first hypothesis is the so-called hygienist hypothesis: in rich countries, the immune system, particularly in early childhood, is less and less exposed to infections (sterilized milk, vaccines, clean water…). This would then develop exaggerated responses against environmental substances responsible for allergies.

We also understood that we could become aware of dietary proteins – make antibodies against these proteins – by being exposed to it through the skin. If the skin is more permeable, as in atopic dermatitis, proteins from the environment can then pass through and induce the production of IgE antibodies. The fact that a child is exposed to a food through the skin route, which is pro-allergenic, before the more tolerogenic oral route, could explain the appearance of allergies. Hence the fact that severe atopic dermatitis is a major risk factor. Children are very exposed, through their skin, to household dust that is found in their beds, on the floors, and armchairs. However, this dust contains significant quantities of food proteins and other allergens.

*According to Séverine Fernandez, president of the French Union of Allergists, interviewed on Franceinfo.