Milk, eggs, peanuts, tree nuts, fish, mollusks, and crustaceans are the foods most frequently involved in food allergies in children. These allergies are on the rise, affecting nearly 6% of children under 15, compared to just 2% two decades ago. What explains this increase in food allergies? Can they be prevented? In recognition of World Allergy Week from June 24 to 29, we spoke with Dr. Guillaume Lezmi, a pediatric allergist at Necker-Enfants Malades Hospital in Paris, to shed light on this important issue.

What is a food allergy?

Dr. Guillaume Lezmi: Food allergies are hypersensitivity reactions to foods triggered by immunological mechanisms. We differentiate between immediate allergies and delayed allergies. Immediate allergies occur within two hours of consuming the food and are caused by allergenic antibodies called IgE. These are known as IgE-mediated allergies. Delayed allergies, which are not IgE-mediated, develop hours after contact with the allergen and can cause chronic symptoms such as digestive disorders (e.g., chronic diarrhea), growth retardation, and bloating.

What are the symptoms of immediate allergies?

The most common symptoms include skin and mucosal reactions such as urticaria (hives), edema (swelling), pruritus (itching), and allergic rhinoconjunctivitis. Severe reactions can lead to anaphylaxis, which includes symptoms like respiratory distress due to bronchospasm or laryngeal edema (Quincke’s edema), fainting, and anaphylactic shock, which can be life-threatening.

What should I do if I experience allergic symptoms after exposure to a food?

Mild skin and mucosal reactions can be treated with oral antihistamines. Severe reactions require one or more intramuscular injections of adrenaline and urgent medical care. After experiencing a reaction, it is crucial to avoid the suspected food and consult a specialist. An allergist can confirm the diagnosis through the patient’s clinical history and tests, such as skin prick tests or measuring specific antibodies in the blood. Non-IgE-mediated allergies, which are often related to milk or wheat, can be harder to diagnose due to non-specific symptoms and a lack of reliable tests.

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

Food allergies can occur without any obvious risk factors, but the main risk factor for IgE-mediated allergies is severe atopic dermatitis. About 20-30% of children with severe atopic dermatitis have food allergies. There is also a slightly increased risk in children of allergic parents.

Can food allergies be prevented in children?

Research has shown that early introduction of peanuts, tree nuts, and eggs during weaning (starting around 4-5 months) can help prevent allergies to these foods. These recommendations apply not only to children at high risk (such as those with severe atopic dermatitis) but also to the general population, as allergies can develop in children without any known risk factors.

Why have food allergies been on the rise in recent years?

The exact reasons are unclear, but several hypotheses have been suggested. The “hygiene hypothesis” posits that in affluent countries, the immune system in early childhood is less exposed to infections due to factors like sterilized milk, vaccines, and clean water, leading to exaggerated immune responses to environmental allergens.

It has also been found that food proteins can sensitize individuals through the skin, especially if it is more permeable, as in the case of atopic dermatitis. Environmental proteins can penetrate the skin and induce the production of IgE antibodies. Exposure to food proteins through the skin before they are introduced orally, which promotes tolerance, might trigger allergies. This might explain why severe atopic dermatitis is a major risk factor. Children are frequently exposed to house dust, which contains significant amounts of food proteins and other allergens, through their skin.