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By the April 12, 2022, the COVID-19 pandemic had resulted in over half a billion people being infected worldwide. There have been 6.1 million deaths directly due to the infection, but the pandemic has had many more short- and long-term pervasive effects on the physical and mental health of the population. Allergic diseases are among the most prevalent noncommunicable chronic diseases in the pediatric population, and health-care professionals and researchers were seeking answers since the beginning of pandemic. Children are at lower risk of developing severe COVID-19 or dying from infection. Allergic diseases are not associated with a higher COVID-19 severity and mortality, apart from severe/poorly controlled asthma. The pandemic disrupted routine health care, but many mitigation strategies, including but not limited to telemedicine, were successfully implemented to continue delivery of high-standard care. Although children faced a multitude of pandemic-related issues, allergic conditions were effectively treated remotely while reduction in air pollution and lack of contact with outdoor allergens resulted in improvement, particularly respiratory allergies. There is no evidence to recommend substantial changes to usual management modalities of allergic conditions in children, including allergen immunotherapy and use of biologicals. Allergic children are not at greater risk of multisystem inflammatory syndrome development, but some associations with Long COVID were reported, although the data are limited, and further research is needed. This statement of the EAACI Section on Pediatrics provides recommendations based on the lessons learnt from the pandemic, as available evidence.

refers to: (1) Brough HA, Caubet JC, Mazon A, Haddad D, Bergmann MM, Wassenberg J, Panetta V, Gourgey R, Radulovic S, Nieto M, Santos AF, Nieto A, Lack G, Eigenmann PA. Defining challenge-proven coexistent nut and sesame seed allergy: A prospective multicenter European study. J Allergy Clin Immunol. 2020 Apr;145(4):1231-1239. doi: 10.1016/j.jaci.2019.09.036. Epub 2019 Dec 20. PMID: 31866098. And (2) Elizur A, Nachshon L, Levy MB, Epstein-Rigbi N, Goldberg MR; Nut CRACKER study group. Translating tree nut cross-reactivity into clinical practice. J Allergy Clin Immunol. 2020 May;145(5):1480-1481. doi: 10.1016/j.jaci.2020.02.003. Epub 2020 Mar 26. PMID: 32223980.

Food allergy is a potentially life-threatening condition affecting almost 10% of children, with an increasing incidence in the last few decades. It is defined as an immune reaction to food, and its pathogenesis may be IgE mediated, mixed IgE and non-IgE mediated, or non-IgE mediated. Potentially all foods can cause food allergy, but a minority of foods are responsible for the vast majority of reactions reported. A good clinical history is crucial for an accurate diagnosis. Allergy tests, including the skin prick test and measurement of specific IgE antibodies, are useful tools in the case of IgE-mediated or mixed allergy but have not been shown to be of any help in delayed allergic reactions to foods.

Children with atopic diseases in early life are frequently found with positive IgE tests to peanuts/tree nuts without a history of previous ingestion. We aimed to identify risk factors for reactions to nuts at first introduction.A retrospective case-note and database analysis was performed. Recruitment criteria were: patients aged 3-16 yr who had a standardized food challenge to peanut and/or tree nuts due to sensitisation to the peanut/tree nut (positive spIgE or SPT) without previous consumption. A detailed assessment was performed of factors relating to food challenge outcome with univariate and multivariate logistic regression analysis.There were 98 food challenges (47 peanut, 51 tree nut) with 29 positive, 67 negative and 2 inconclusive outcomes. A positive maternal history of allergy and a specific IgE5 kU/l were strongly associated with a significantly increased risk of a positive food challenge (OR 3.73; 95% CI 1.31-10.59; p = 0.013 and OR 3.35; 95% CI 1.23-9.11; p = 0.007, respectively). Adjusting for age, a three year-old with these criteria has a 67% probability of a positive challenge. There was no significant association between types of peanut/tree nut, other food allergies, atopic conditions or severity of previous food reactions and positive challenges.We have demonstrated an association between the presence of maternal atopic history and a specific IgE5 kU/l, with a significant increase in the likelihood of a positive food challenge. Although requiring further prospective validation these easily identifiable components should be considered when deciding the need for a challenge.

Molecular allergology is a breakthrough science that enables the quantification of IgE and IgG antibodies against individual allergen protein components at a molecular level. The diagnosis of IgE-mediated allergic disorder among children is based on clinical history and sensitization demonstrated through an allergy test. Identifying whether the sensitization is primary (species specific) or a result of cross-reactivity to proteins with similar protein structures helps the clinician to judge the risk of allergic reaction. This is possible today because allergen component tests are now available for clinicians to use in everyday practice. This article focuses on clinical utility through the prediction of cross-reactivity or primary sensitization, estimation of the risk of reaction to heated food and the risk of severe clinical symptoms.

Once administered, a drug can activate the immune system by various mechanisms and lead to a large range of clinical manifestations closely related to the type of immune reaction elicited. Administration of the drug can classically result in an immunoglobulin E (IgE)-type sensitization, but can also result in more complex activation of the immune system potentially resulting in severe syndromes, such as the drug-induced hypersensitivity syndrome (DIHS). Although there has been a major increase in our knowledge over the last years, the exact mechanisms of drug allergy are not well understood for most clinical manifestations. A complex interaction between individual characteristics, environmental factors, and the drug itself is usually responsible for adverse reactions to drugs. In this educational review series, we described three cases of drug allergy: first, a child with a typical IgE-mediated drug allergy, second, a child with a non-immediate reaction to penicillin, and in the third patient, we will discuss the drug-induced hypersensitivity syndrome, which is rare but potentially fatal. These cases are correlated to the immune mechanism potentially involved.

Primary care physicians will conduct allergy diagnosis based on the history provided by the patient. In case of a possible IgE type allergy, investigations will be made by skin tests or measurement of specific IgE antibodies in the serum. Interpretation of positive tests will have to consider possible sensitizations in absence of allergic symptoms that should not lead to inadequate therapeutic measures or diet. This review will provide to primary care physicians guidance to choose the best method in the appropriate situations for allergy diagnosis.

Although food hypersensitivity might be divided in IgE- and non-IgE mediated food allergy, there is a large body of evidence implicating T lymphocytes overall in the pathogenesis of food allergy. Priming of naive T cells will occur mainly in Peyer's patches (PP), where surface receptors (l-selectin, CCR7 and CXCR4) will help to initiate diapedesis of the cells to the submucosa. Various antigen-presenting cells (e.g. dendritic cells, M cells) will present food antigen-derived epitopes and initiate either non-responsiveness, or a food-mediated immune response. Food-specific memory T cells express various surface receptors such as the alpha4beta7-integrin, or the cutaneous lymphocyte antigen. It is speculated, that they might also express specific chemokine receptors (CCR4, CCR7 or CCR9). Organ-specific homing will be facilitated through the corresponding receptors (i.e. MAdCAM-1 in the gut, VCAM-1 or fibronectin in other mucosal organs, or E-selectin in the skin). Locally secreted chemokines might help to attract T cells through their corresponding chemokine receptors. Finally, potential T-cell directed therapeutic interventions (peptide-derived immunotherapy, DNA vaccination, or strategies preventing T cells from trafficking to target organs) are discussed.