Role of food allergy in asthma in childhood.

Atopy is the major predisposing factor for asthma identified up to now, and allergen exposure, particularly indoor allergens, is considered as a causal factor for asthma. Food allergy is frequently underestimated in association with asthma, however food allergy has been shown to trigger or exacerbate broncho-obstruction in 2 to 8.5% of children with asthma. There is also evidence that double-blind placebo-controlled oral challenge is able to increase unspecific bronchial hyperresponsiveness. Sensitization to food can occur early in life involving T cell response, mainly of the Th2 phenotype, but also IgE-mediated hypersensitivity. Moreover, it has been shown that sensitization to food allergens early in life is a risk factor for sensitization to inhalent allergens and respiratory symptoms later on. Epidemiological studies suggest that changes in the dietary composition, such as trans-fatty acids, could be involved in the increase of asthma prevalence. The introduction of formula during the first trimester of life increases the risk of having asthma. The diagnosis of food allergy associated with asthma is not easy, nevertheless is important for allergists, pulmonologists and paediatricians to consider food allergy in children with respiratory symptoms, especially when asthma symptoms start early in life and when they are associated with other manifestations of food allergy. Children sensitized to cow's milk proteins and also having atopic eczema are at higher risk for asthma. Since avoidance of the offending food is the first step in the management of children with asthma associated with food allergy, a careful identification should be done in order to avoid unnecessary elimination of foods.