Approximately 5% of young children and 3–4% of adults exhibit adverse immune responses to foods in westernized countries, with a tendency to increase. The pathophysiology of food allergy (FA) relies on immune reactions triggered by epitopes, i.e. small amino-acid sequences able to bind to antibodies or cells. Some food allergens share specific physicochemical characteristics that allow them to resist digestion, thus enhancing allergenicity. These allergens encounter specialized dendritic cell populations in the gut, which leads to T-cell priming. In case of IgE-mediated allergy, this process triggers the production of allergen-specific IgE by B cells.
Tissue-resident reactive cells, including mast cells, then bind IgE, and allergic reactions are elicited when these cells, with adjacent IgE molecules bound to their surface, are re-exposed to allergen. Allergic reactions occurring in the absence of detectable IgE are labeled non-IgE mediated. The abrogation of oral tolerance which leads to FA is likely favored by genetic disposition and environmental factors (e.g. increased hygiene or enhanced allergenicity of some foods). For an accurate diagnosis, complete medical history, laboratory tests and, in most cases, an oral food challenge are needed. Noticeably, the detection of food-specific IgE (sensitization) does not necessarily indicate clinical allergy. Novel diagnostic methods currently under study focus on the immune responses to specific food proteins or epitopes of specific proteins. Food-induced allergic reactions represent a large array of symptoms involving the skin and gastrointestinal and respiratory systems. They can be attributed to IgEmediated and non-IgE-mediated (cellular) mechanisms and thus differ in their nature, severity and outcome. Outcome also differs according to allergens.
Whether breastfeeding protects against the development of allergic disease has been a frequent subject of study and debate for 75 years. This paper summarizes the published evidence concerning the risks of atopic dermatitis, asthma, allergic rhinitis, positive allergen skin tests, and food allergy associated with infant feeding. The summary is based largely on systematic reviews and meta-analyses carried out by other authors. In addition, I also incorporate the evidence from our long-term follow-up of Belarusian children participating in a cluster-randomized trial of a breastfeeding promotion intervention.
The need for allergy prevention strategies has never been greater. Surging rates of food allergy and eczema are now adding to the already substantial burden of asthma and respiratory allergic diseases. The parallel rise in many other immune diseases suggests that the developing immune system is highly vulnerable to modern environmental changes. These strong environmental pressures may be one reason why simple allergen avoidance strategies have not been successful. Another more recent strategy to curtail the allergy epidemic has been to identify factors associated with modern lifestyle that may be causally linked with allergic disease, in an attempt to restore more favourable conditions for immune tolerance during early development. More hygienic conditions and disruption of microbial exposure have prompted strategies to restore this balance using probiotic and prebiotic supplements. Modern dietary changes linked with allergic diseases have prompted supplementation studies to assess the preventive merits of specific immunomodulatory dietary nutrients such as polyunsaturated fatty acids. Other nutrients such as antioxidants, folate, and vitamin D are also currently under investigation. Modern environmental pollutants have also been associated with adverse effects on immune development and the risk of disease. While many of these avenues have provided some promise, they have not yet translated into specific recommendations. Current evidence-based guidelines for allergy prevention remain limited to avoidance of cigarette smoke, promotion of breastfeeding and the use of hydrolysed formula when breastfeeding is not possible. Allergen avoidance strategies have been largely removed from most guidelines. It is hoped that a number of ongoing studies will help provide clearer recommendations around the use of probiotics, prebiotics, specific dietary nutrients and the role of early introduction of allergenic foods for the promotion of tolerance. Despite the current uncertainties, prevention remains the best long-term strategy to reduce the growing burden of allergic disease.
Clinical trials have demonstrated that the risk of developing atopic dermatitis is reduced when using hydrolysed formulas to feed infants with a documented risk of atopy (i.e. an affected parent and/or sibling) when breastfeeding is not practised. However, little is known about the cost-effectiveness of using hydrolysed formulas. Consequently, economic analyses in 5 European countries (Denmark, France, Germany, Spain and Switzerland) have evaluated the costs and cost effectiveness of a specific brand of 100% whey-based partially hydrolysed infant formula, NAN-HA _ (PHF-W) compared with a cow’s milk standard formula (SF) in the prevention of atopic dermatitis in at-risk children. This review synthesises the findings of these studies. Cost-effectiveness analyses (CEA) used a decision-analytic model to determine treatment pathways, resource utilisation and costs associated with the management of atopic dermatitis in healthy at risk newborns who were not exclusively breastfed. The model had a 12-month horizon and applied reimbursement rates of 60–100% depending on the country. Outcomes were considered from the perspective of the public healthcare system (e.g. the Ministry of Health; MOH), family and society. The final outcome was the incremental cost-effectiveness ratio per avoided case of atopic dermatitis (ICER) for PHF-W versus SF. A cost-minimisation analysis was also performed to compare PHF-W with extensively hydrolysed formulas (EHF). The basecase CEA produced ICERs per avoided case for PHF-W versus SF of EUR 982–1,343 (MOH perspective), EUR –2,202 to –624 (family perspective) indicating savings, and EUR –1,220 to 719 from the societal perspective. The main costs related to formula (MOH and society) and time loss (family). In the cost minimisation analysis, PHF-W yielded savings of between EUR 4.3 and 120 million compared with EHF-whey when the latter was used in prevention. In conclusion, PHF-W was cost effective versus SF in the prevention of atopic dermatitis and cost saving compared with EHF when used in prevention.