Food allergies in connection with allergic respiratory diseases

Food allergies seem to be of particular importance in the development of asthma and allergic rhinitis, suggesting a French study published in the "Allergy" review and confirm the theory of the "allergic march".

According to the authors, this study is the first to assess the prevalence of sensitization to major food allergens and symptoms of food allergy with a large sample of French schoolchildren.

Although food allergies are a significant health problem, epidemiological studies in the general population are few, report Dr. Celine Pénard Morand, the Inserm Unit 472 (Epidemiology of respiratory diseases), and colleagues. Indeed, testimonies on the declarative mode, a diagnosis of food allergy are difficult to confirm a large scale, because the necessary tests show heavy to implement consistently.

To highlight objectively sensitization to food allergen must make skin tests and specific IgE, while the involvement of a food in a food allergy can be proved by means of a test controlled food challenge and performed double-blind.

This team of French researchers sought to determine the proportion of children in school with this type of allergic diseases, which can lead to skin disorders, gastrointestinal or respiratory. Another objective of their study: clarify the relationship of food allergies with respiratory symptoms of allergy (asthma, allergic rhinitis, bronchial hyperresponsiveness to exercise) to determine the extent to which these symptoms can be the result of sensitization to inhalant allergens.

In this context, nearly 6,700 children aged 9 to 11 years were recruited from a hundred chosen so random in six French cities schools. Young participants underwent a complete physical examination, with a possible search for one of the three major food allergens characteristics of this age group (egg, fish, peanuts) with skin testing and evaluation awareness by via a standardized protocol-induced airway hyperresponsiveness by exercise. Standardized questionnaires were also submitted to the parents of the young participants to assess the presence of asthma, allergic rhinitis and clinical symptoms of food allergies.

Based on these data, it was found that 2.1% of the participating children had already presented the characteristic symptoms of a food allergy after eating a particular food. The proportion of participants in a food allergen sensitized (that is to say having at least a positive skin test) was meanwhile elevated to 1.9%. The combination of these two groups has enabled the authors to note that 0.1% of children they have taken to meet these criteria and therefore could be considered as suffering from respiratory allergy confirmed by a skin test.

Analysis of the various results of this survey showed that asthma and allergic rhinitis showed significantly more frequent in children with a food allergy or sensitization. The association between food allergic reactions and allergic respiratory diseases remained after adjustment to take into account the influence of age, sex, passive smoking, or a family history of allergic diseases, the authors report.

However, the link between asthma and allergic rhinitis and food allergy awareness or can not be fully explained by the existence of respiratory manifestations of food allergy or sensitization to inhalant allergens, the authors note.

The results of this study, which highlight the importance of food allergy in the development of asthma and allergic rhinitis, suggest that during childhood, food awareness could promote awareness of inhalant allergens, which in even represent a major risk factor for asthma and allergic rhinitis.

This work thus confirms the hypothesis of "allergic march", an expression that experts use to describe the fact that with age, the manifestations of allergy change and often evolve into more serious forms.

Thus, the infant is more prone to food allergies, which is most often manifested by gastrointestinal symptoms (vomiting, diarrhea ...) or skin (eczema, hives ...). Asthma is more common then from about five years, while at the age of ten, allergic rhinitis or "hay fever" are the predominant forms.