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Food allergies in children

Dr. Philippe Eigenmann, Pediatric Allergist
Children's Hospital, Geneva

Food allergy or food intolerance ?

Are all children allergic? This provocative question is justly raised when listening to the media, to discussions between parents and to the population's fears. Of course, the answer is negative, because even if the word allergy is evoked for all kinds of gastrointestinal symptoms, it actually defines a very specific type of diseases.

Allergy is an overreaction of the immune system to food, pollen, ... which is usually not harmful to the body and which should therefore be tolerated. Frequent food intake in our lifestyle and our need to find a culprit for lesser evils explains why foods are so frequently evoked. Actually, we suffer more often from intolerances, which reflect difficulty digesting certain foods. Intolerances are usually temporary, whereas allergies remain for at least several months and up to several years. Furthermore, it is estimated that 2.5 % of children suffer from food allergies, while the figure goes down to around 1.2 % in adults.

How to spot a food allergy

We can distinguish children food allergies that occur especially during the first year of life from those that occur later on and are very similar to adult allergies.

Infants with a family risk of allergy usually start their allergic history with atopic eczema (=allergic eczema). If an allergic constitution is the primary cause of this disease, an allergy to a certain type of food can aggravate eczema in about 30% of these children. If the food is removed from the child’s diet, the eczema will improve, but it will not completely disappear since the allergic constitution of the child cannot be changed. Other infants present their first food allergy in the form of hives after a bottle of milk. When symptoms are severe, with symptoms such as faintness and breathing difficulties, the reaction is called an anaphylactic reaction and requires quick care in an emergency center. In some infants, food allergy manifests itself exclusively as gastrointestinal symptoms such as vomiting, diarrhea, or blood in the stool.

Later on, when children are preschool or school age, food allergy will manifest itself most frequently very quickly after taking the food and will take the form of hives or anaphylactic shocks. The rapid onset of the reaction often allows easy identification of the food by the patient or his parents.

Eggs or milk are often involved in young children’s food allergies. The allergy prognosis is then generally good with spontaneous disappearance of the allergy in 2-3 years. Older children suffer more frequently from allergies to peanuts, tree nuts, fish, ... which tend to persist longer.

Food allergy management

Any allergy suspicion should be followed by an accurate diagnosis. Indeed, as most food reactions are due to intolerance (reactions limited in time and often permitting the consumption of the food in small quantities), many diets are not justified and may require a lot of work, or even cause nutritional deficiencies. During the consultation, the doctor will evaluate the history of the reactions and the likelihood that it is indeed an allergy. He will then confirm the diagnosis by either blood screening or skin testing. In a child who has a significant allergic predisposition, these tests can be difficult to interpret due to false positive results. A challenge test in a hospital may then sometimes be necessary.

In the absence of definitive treatment for food allergies, a strict elimination diet remains the only recommendation. The diet has two purposes: it prevents a new reaction, but it also fosters, in allergies with a good prognosis (milk, eggs), faster healing since the immune system ‘forgets’ its tendency to react unpredictably. The involvement of a dietician can often provide essential practical advice to the patient.

The classic and definitive treatment of respiratory allergy (‘desensitization’) is unfortunately not only ineffective in the case of food allergies, but it can also be dangerous since allergic reactions can have severe side effects. However, many current studies offer hope to our patients for an effective treatment of food allergies in the not too distant future.

Finally, the management of food allergies also includes explanations on how to treat an allergic reaction. It implies that the patient (or his parents/caretakers in the case of children) must always have at hand, medicine to treat allergic reactions, such as antihistamine and/or an epinephrine auto-injector. When the allergic reaction is severe, the proper use of these drugs can save lives.

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