The COVID-19 pandemic has surprised the entire population. The world has had to face an unprecedented pandemic. Only, Spanish flu had similar disastrous consequences. As a result, drastic measures (lockdown) have been adopted worldwide. Healthcare service has been overwhelmed by the extraordinary influx of patients, often requiring high intensity of care. Mortality has been associated with severe comorbidities, including chronic diseases. Patients with frailty were, therefore, the victim of the SARS-COV-2 infection. Allergy and asthma are the most prevalent chronic disorders in children and adolescents, so they need careful attention and, if necessary, an adaptation of their regular treatment plans. Fortunately, at present, young people are less suffering from COVID-19, both as incidence and severity. However, any age, including infancy, could be affected by the pandemic. Based on this background, the Italian Society of Pediatric Allergy and Immunology has felt it necessary to provide a Consensus Statement. This expert panel consensus document offers a rationale to help guide decision-making in the management of children and adolescents with allergic or immunologic diseases.

The problem of respiratory allergies concerns about 40% of the world population, with a significant impact on the quality of life for those who suffer from it. The most common clinical manifestations are allergic rhinoconjunctivitis and asthma, determined by genetic and environmental factors that can alter lung development in children and adolescents. Air pollution has a significant responsibility in this. 1 Among the main pollutants are certainly PM10 (particulate matter) with an aerodynamic diameter of 10 µm and <2.5 µm (PM2.5) and ultrafine particulate matter (UFP), which are particles <0.1 µm. 2 European legislation has set the "recommended" maximum concentration levels at 50 and 25 µg/ m 3 for the annual average, respectively, for PM10 and PM2.5. The particulates are produced from anthropogenic sources such as traffic, combustion processes, and industrial gas activities, and from natural sources, such as marine spray, crustal minerals, and forest fires. It also has a secondary component that is formed in the atmosphere and which, especially in the urban area, constitutes a significant fraction. Dimensions, surface, and composition of the polluting particle determine the potential risk for a patient who is exposed regularly. 3-5 Early exposure, in gestational or neonatal times, for example, can trigger epigenetic mechanisms, such as DNA methylation and oxidative stress, which increase the risk of adverse outcomes at birth and the subsequent development of asthma and allergic rhinitis. 6 Another powerful

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Airborne particulate (PM) components, especially those deriving from anthropogenic activities such as the combustion of fossil fuels, can induce oxidative stress triggered by reactive oxygen species (ROS). The reported associations between asthma morbidity and exposure to air pollutants, mainly PM 2.5, could be related to the oxidative potential of PM capable of inducing oxidative stress and airways inflammation, which are the hallmarks of asthma disease. 1 However, the oxidative potential of PM may be, in part, independent of the PM mass. Therefore, a potentially small fraction of chemical components can even produce the same effects. Many aerosol components have redox activities (e.g., polycyclic aromatic hydrocarbons (IPA), transition metals), and epidemiological associations can be influenced if the analyzes are based only on mass concentrations and not on the chemical characterization of PM2.5 and/or of PM10. Few studies have addressed this possibility by characterizing the overall oxidative potential of PM2.5 and correlating it with daily changes in fractional exhaled nitric oxide (FENO), which is a pivotal biomarker of airway inflammation in children with asthma. 2 One of the most used methods to evaluate the oxidative potential of PM components in acellular mode is the dithiothreitol (DTT) assay. DTT assay is used to demonstrate the ability of PM to transfer electrons from the DTT to oxygen, resulting in the generation of superoxide. DTT is an indicator of redox activity, positively correlated to the content of IPA, organic carbon (OC), metals, and partially inhibited by metal chelators. 3 DTT consumption is highest in ultrafine PM (<0.15 µm) and combustion sources of organic chemicals and transition metals, which have a high oxidative potential. The intracellular response to exposure to PMs with high OP (oxidative potential) consists in the production of ROS, with the parallel activation of signals for the synthesis of pro-inflammatory cytokines, determining an