Background: Ambient air pollution has been linked to the increasing prevalence of allergic diseases in children. Exposure to air pollution increases the incidence of asthma and allergic rhinitis and is also known to be associated with inhalant allergen sensitization. Methods: From 2011 to 2024, we retrospectively analyzed the medical records of 313 children in Busan, Korea, with asthma and allergic rhinitis who underwent allergen testing for house dust mites (Dermatophagoides pteronyssinus, D. farinae), animal dander, tree pollen, grass pollen, weed pollen, mold (Alternaria alternata), and cockroach. Ambient air pollutant concentrations of O3, SO₂, CO, NO₂, particulate matter (PM) ≤10 µm (PM10) and PM ≤2.5 µm (PM2.5) were obtained from measurement sites located near the residences of the study subjects. Results: Among the 313 subjects, 94 had asthma, 137 had allergic rhinitis, and 82 had combined asthma and allergic rhinitis. In children who experienced allergic rhinitis symptoms, changes in PM10, PM2.5, maximum SO2 concentration, and maximum NO2 concentration showed positive correlations (correlation coefficients, 0.60, 0.56, 0.64, and 0.49, respectively). In cases of allergic rhinitis accompanied by inhalant allergen sensitization, changes in PM10, PM2.5, CO, NO2, maximum SO2 concentration, maximum CO concentration, and maximum NO2 concentration also showed positive correlations (correlation coefficients, 0.64, 0.60, 0.56, 0.49, 0.52, 0.71, and 0.60, respectively). Conclusions In this study, several air pollutants were associated with allergic rhinitis symptoms in children residing in Busan, and a broader range of air pollutants was associated with allergic rhinitis accompanied by inhalant allergen sensitization.

Purpose: Since the start of the coronavirus disease 2019 (COVID-19) pandemic, various variants of concern have emerged. We divided the representative COVID-19 mutation period into four waves and aimed to analyze the clinical and laboratory features of children with COVID-19 from pre-mutation wave to the middle of omicron wave. Methods: We retrospectively reviewed the medical records of hospitalized patients aged ≤19 years with laboratory confirmed COVID-19. Clinical and laboratory findings during premutation (February 1st 2020 to September 30th 2020), alpha/beta (October 1st 2020 to May 31st 2021), delta (June 1st 2021 to October 31st 2021), and omicron (November 1st 2021 to May 31st 2022) waves were compared. Results: Among total 827 patients, 163 (19.7%) were asymptomatic, and the frequency of fever and cough was 320 (38.7%) and 399 (48.2%), respectively. The proportion of fever ≥38.5°C was observed to be high during the omicron wave in the age group under 12 years.Lymphopenia was observed highly in the omicron wave in the age group under 12 years, and in the delta wave in the age group older than 12 years. Neutropenia was highly observed in the delta wave in the 0–4 years age group. Conclusions There were distinct characteristics during all epidemic waves of COVID-19.Children with COVID-19 had more frequent persistent fever during delta wave and children during the omicron wave had a higher peak fever.