Over the last two decades, the prevalence of food allergies has registered a significant increase in Westernized societies, potentially due to changes in environmental exposure and lifestyle. The pathogenesis of food allergies is complex and includes genetic, epigenetic and environmental factors. New evidence has highlighted the role of the intestinal microbiome in the maintenance of the immune tolerance to foods and the potential pathogenic role of early percutaneous exposure to allergens. The recent increase in food allergy rates has led to a reconsideration of prevention strategies for atopic diseases, mainly targeting the timing of the introduction of solid foods into infants' diet. Early recommendation for high atopy risk infants to delay the introduction of potential food allergens, such as cow's milk, egg, and peanut, until after the first year of life, has been rescinded, as emerging evidence has shown that these approaches are not effective in preventing food allergies. More recently, high-quality clinical trials have suggested an opposite approach, which promotes early introduction of potential food allergens into infants' diet as a means to prevent food allergies. This evidence has led to the production of new guidelines recommending early introduction of peanut as a preventive strategy for peanut allergy. However, clinical trials investigating whether this preventive dietary approach could also apply to other types of food allergens have reported ambiguous results. This review focuses on the latest high-quality evidence from randomized controlled clinical trials examining the timing of solid food introduction as a strategy to prevent food allergies and also discusses the possible implications of early complementary feeding on both the benefits and the total duration of breastfeeding.
Keywords: allergy; breastfeeding; children; complementary foods; food allergy; microbiome; tolerance.