Food allergy and atopic dermatitis

Food allergy and breast-feeding

Breast-feeding is currently recommended as the optimal source of nutrition for infants; however, it is known that some individuals can excrete enough food antigens in breast milk to result in allergic reactions in infants, especially those already highly sensitized. These reactions can include non-immunoglobulin E (IgE) mediated reactions, such as atopic dermatitis or gastrointestinal symptoms, and IgE-mediated reactions, such as anaphylaxis, although rare. Food reactions in infants who are breast-fed is a unique challenge because identifying the culprit foods may be more difficult and special consideration must be taken in ensuring proper nutrition during periods of food avoidance for both the infant and mother. This article reviews what is currently known about food allergy in infants who are breast-fed as well as offers insights into a proposed evaluation.

Classification of adverse food reactions

Foods can induce adverse reactions by a variety of mechanisms. An understanding of the characteristic signs and symptoms and the related mechanisms of adverse food reactions allows the clinician to efficiently diagnose and treat patients. Adverse reactions to foods can be classified based on whether there is a nonimmunologic or immunologic basis for symptoms. Food intolerance, or a nonimmunologic reaction, includes a range of responses to foods that result primarily from an individual's intrinsic inability to metabolize a component of the food, e.g., lactose sugar in dairy products. Other nonimmunologic adverse reactions may be attributed to food toxins or pharmacologic properties pharmacologic properties of foods themselves. Immunologic adverse reactions, in contrast, involve immune responses to food and are termed food allergy. Food allergy may further be categorized based on the underlying immunopathophysiology as immunoglobulin E (IgE) mediated, non-IgE mediated, or cell mediated. Some chronic allergic responses involve a combination of immune mechanisms. This review provides a general classification system for adverse food reactions and describes specificconditions.

Food allergy epidemiology and racial and/or ethnic differences

In recent decades, immunoglobulin E (IgE) mediated food allergy has become a growing public health concern. Converging evidence from cross-sectional prevalence studies, health care utilization records, and cohort studies indicate that food allergies are increasingly prevalent and often severe. Although IgE-mediated food allergy has long been considered a predominantly pediatric concern, analysis of recent self-reported data suggests that food allergies may be more prevalent among adult populations than previously acknowledged, with many reported cases of adult-onset allergies as well as persistent childhood-onset allergies. Results of studies also suggest that food allergy-related health care utilization is increasing as more individuals seek emergency treatment for food-induced anaphylaxis. Analysis of epidemiologic data also indicates that the burden of food allergies is unequally distributed. Published prevalence rates are highest in Western countries, e.g., the United States, United Kingdom, and Australia. Within these countries, there also is heterogeneity across racial and/or ethnic groups, with non-White and second-generation immigrant populations disproportionately affected. Importantly, such observations can shed light on the etiology of food allergy and inform improved clinical management, treatment, and prevention efforts. For example, there is a growing consensus that earlier introduction of allergenic foods, e.g., peanut, promotes oral tolerance and can dramatically reduce food allergy risk. In addition, much attention has been paid to the potentially deleterious effects of cutaneous allergen exposure, e.g., through eczematous skin, which can skew the immune response away from tolerance and toward allergic sensitization, thereby increasing food allergy risk. Furthermore, there is a growing appreciation for the potential protective effects of diverse microbial exposures, given mounting evidence for the immunomodulatory effects of the human microbiome. Also, when considering the geographic variability in the prevalence of certain food and environmental allergies as well as their structural similarities at the molecular level, it is believed that co-sensitization between food and environmental allergens may be a key driver of rising food allergy prevalence.

Food allergy prevention, including early food introduction

As the prevalence of immunoglobulin E (IgE)-mediated food allergy continues to increase without an imminent cure, prevention has become an urgent need. A breakthrough study that shows that early consumption of peanut can prevent the development of peanut allergy has led for a push in early interventions. Theories associated with the increasing prevalence of food allergy lend themselves to areas of potential intervention, e.g., age at time of food introduction, infant feeding practices, microbiome influences, diet composition, vitamin D deficiency, and increasing rates of eczema. This review focused on the available data from studies that investigated early interventions to decrease the risk of food allergy.