Dietary side effects represent an increasingly prevalent public health issue worldwide. The proper illustration of the differences between food allergies, which involve immunological mechanisms, either IgE or non-IgE mediated, and food intolerances, which appear without immune involvement, is critical for establishing subsequent diagnostic and therapeutic options. Current medical research aims to study the pathogenesis of food allergies in order to develop new therapeutic tools.
The existence of an abundance of modulating environmental factors, which act upon a genetic substrate entail a wide phenotypic variability of allergic reactions that leads to complex clinical manifestations. A comprehensive and correct diagnosis followed by prompt, adequate preventive measures, an adequate therapeutic approach, allow the maintaining of a proper nutritional status and psycho-behavioural development, the goal being to establish good quality of life for these patients.
Food allergies are a major public health problem. Statistic data concerning the incidence and prevalence of food allergies in children vary. They depend on multiple parameters, such as age, sex, diet, existing comorbidities, genetic factor, socioeconomic factors, geographical area etc. In the general population, food allergies have a medically documented incidence of 10.8%, affecting around 8% of children and 3.7% of adults . Approximately 6%–8% of children under the age of 2 will develop this disorder , which in 80% of cases will recede until school age . The vast majority of proteic food allergies (60%) are IgE mediated. In most cases, these appear with exposure to a single type of food and in 35% of cases multiple food allergies are noted . The most frequent type of food allergy in the first years of life is milk protein allergy, which affects 21.1% of children with documented food allergies .
The trigger of the allergic reaction involves the interaction between food allergen, gastrointestinal barrier and immune system. Gastrointestinal tract is a complex ecosystem, its functions and components ensuring the absorption of nutrients from the ingested food. Furthermore, it is involved in the intestinal immune activity by averting pathogenic agents from entering the body. The intestinal immune components consist of gut-associated lymphoid tissue (GALT), mucosa associated lymphoid tissue (MALT), secretory IgA, effector immune cells (helper and suppressor T cells, macrophages, plasmocytes). Payer’s patches, the enterocytes and the intercellular junctions have the role of macromolecular passageway . The non-immunologic barrier consists of: gastric pH, intestinal mucus, commensal microflora, lactoferrin etc. These components are underdeveloped in infants and toddlers. Therefore, enzymatic activity is reduced and the IgA secretion rate reaches normal values around the age of 4 years, features that determine a high prevalence of food allergies in these age groups . The most significant risk factors involved in developing food allergies are immaturity and the alteration of the intestinal immune system, the immaturity of the intestinal nervous system, high intestinal permeability, the imbalance between the intestinal mucosa and the microflora, genetic imbalances (of the IgE receptors, the synthesis of cytokines etc.), gastrointestinal infections.
The most frequently encountered potentially allergenic foods (which determine over 90% of food allergies) are milk and dairy products, eggs, fish, soy, wheat, peanuts, shellfish, hard-shelled fruits (nuts, hazelnuts, pistachio, almonds, cashew etc.) .
The clinical spectrum of food allergies is varied, depending on certain characteristics of the allergen (quantity, preparation, ingestion of other foods, possible cross reactivity etc.), of the host (age, health condition, prior sensitisation, nutritional status, comorbidities, the simultaneous ingestion of alcohol – which increases allergen absorption) and of the immune or non-immune mechanism that triggers the reaction. Clinical manifestations may involve various organs and systems (skin and subcutaneous tissue, respiratory system, cardiovascular system, digestive tract etc.) . The most severe manifestations of food allergies are anaphylactic shock (IgE mediated food allergy) and food protein induced enterocolitis (non-IgE mediated food allergy).
Diagnostic evaluation is mandatory in any child with signs and symptoms that suggest food allergy and in children already diagnosed with atopic dermatitis, eosinophilic gastroenteritis, gastreosophageal reflux whose symptoms do not improve following the administration of specific treatment . Food allergies are characterised by great phenotypic variability. The diagnosis is difficult and in order to document it one must bring together a detailed history of disease, clinical data, specific paraclinical tests, as well as take into consideration child’s response to therapy.
The management of food allergies includes pre and postnatal preventive measures, avoidance of dietary allergens and medical treatment when life-threatening symptoms occur (anaphylactic shock).
Prevention is the most efficient “therapeutic” approach. Identifying and eliminating environmental factors are the key to decrease food allergy prevalence. This has to be started in the intrauterine life by establishing a balanced diet rich in fibre, fruits and vegetables, as well as by providing dietary supplements to the expecting mother (vitamins, fish oil etc.) and by her avoidance of the risk factors that are involved in the development of allergies (smoking, crowded spaces, environmental pollutants etc.). The exclusion of any type of food from the pregnant woman’s diet before birth or during breast-feeding (including foods that are potentially allergenic) is not recommended .
There is modest evidence suggesting that administration of probiotics (Lactobacillus Rhamnossus etc.) to mothers-to-be during pregnancy or to nursing mothers helps to prevent atopic dermatitis during the first months of life. After birth, breastfeeding is recommended as the only source of nutrition during the first 4–6 months of life. Exclusive breast milk feeding exerts long-term protective effects against allergic disorders, including atopic dermatitis, by inducing oral tolerance. In those cases when breastfeeding is not possible, partially hydrolyzed formulas are recommended for infants with a family history of atopy .
At present, there are no specific recommendations for at-risk infants concerning introducing solid foods. Diversification is recommended after 4 months, but before 7 months. There are no benefits in delaying introducing solid foods or in avoiding allergenic foods in the first year of life. Recent studies have shown that earlier consumption of allergenic foods is more beneficial for primary prevention than delaying the introduction of certain foods in the baby’s dietary diversification scheme . In this regard, fish consumption in the first year of life seems to exhibit a protective influence.
Vitamin D plays an important role in the regulation of the immune system. The alteration of 25(OH)D3 bioavailability seems to be of significant importance in the development of allergies, therefore vitamin D deficiency correlates with an increase in the risk of developing allergies .
The hygiene theory describes the protective influence of early exposure to microorganisms with regard to allergic disorders. Numerous studies have shown that postnatal exposure to pathogens and infections may influence the host’s microbiota and immune system, elements that play a key role in the immune response and the development of oral tolerance .
Conclusion Food allergies and the effects they exert represent a topic of major importance in paediatric medical practice, especially given the fact that their prevalence is rising.The key elements of managing food allergies are: avoidance of the trigger, initiation of an adequate diet and prompt administration of emergency medication in severe, life threatening forms. The essential therapeutic objective is to maintain an optimal nutritional status, with close monitoring of the diet and of growth parameters.
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