Background: Recurrent wheeze in infancy is common; although symptoms often resolve, some children develop persistent disease. To better capture clinical heterogeneity, we analyzed wheeze trajectories based on symptom frequency rather than simply recording presence or absence. Objective: To identify distinct wheeze phenotypes in 1-year-old children with recurrent wheeze based on longitudinal wheezing frequency trajectories. Methods: We conducted a two-year, multicenter prospective cohort study involving children aged 12–23 months with recurrent wheeze at 27 sites in Japan. Monthly caregiver-reported wheeze frequency was collected, and trajectories were classified using latent class growth analysis. Clinical characteristics, environmental exposures, and biomarkers were assessed at enrollment and age 3. Ordinal and binary logistic regression analyses were performed to identify risk and protective factors. Results: Among 253 enrolled children, 219 completed follow-up. Four trajectories were identified: Early-Resolving (24.2%), Low-Frequency with Mid-Peak (57.1%), Persistent High-Frequency (12.8%), and Late-Peaking High-Frequency (5.9%). The latter two groups showed greater symptom burden, including more frequent corticosteroid use and interference with daily activities. Ordinal logistic regression showed that parental allergic rhinitis and pet ownership were associated with lower odds of more severe trajectories. Binary logistic regression comparing high- (Clusters 3–4) versus low-frequency (Clusters 1–2) groups revealed parental smoking as a strong risk factor (OR 5.49), while allergic rhinitis (OR 0.12) and pet ownership (OR 0.11) remained protective. Conclusions: High-frequency wheeze trajectories were linked to greater clinical burden. Early identification of at-risk children and targeted environmental interventions—particularly avoidance of passive smoking—may reduce morbidity in early-onset recurrent wheeze.

Background: Accidental allergic reactions (AAR) in children are under-studied, especially with precise pediatrician-based exact diagnoses and follow-ups. This study aimed to assess the prevalence and risk factors for AAR in Japanese children with immediate-type food allergies. Methods: This single-center study included children with immediate-type hen’s egg (HE), cow’s milk (CM), wheat, or peanut allergy who had been followed-up regularly at a national center specialized for allergy in Japan. Low-dose reactivity was defined as allergic reactions to a low dose of ≤250, ≤102, ≤53, or ≤133 mg HE, CM, wheat, or peanut protein, respectively. From January to December 2020, pediatricians followed the AAR experience every 2–4 months. Risk factors for AAR were analyzed using multiple logistic regression. Results: Of the 1096 participants, 609, 457, 138, and 90 had HE, CM, wheat, and peanut allergies, respectively. In this cohort, the median age was 5.0 years, 39% had completely eliminated allergenic food, and 24% had low-dose reactivity. The annual AAR rate was 0.130 in all sub-cohorts. Moderate and severe symptoms occurred in 50% and 0.7%, respectively, of children who experienced AAR. Multiple logistic regression revealed that low-dose reactivity was a significant risk factor for AAR in the overall, HE, and CM cohorts, respectively ( p <0.001, p = 0.029 and 0.036). Conclusion: In Japanese children with immediate-type food allergies, the annualized rate of AAR was relatively low; however, half of the participants with AAR had moderate to severe symptoms. Children, especially those with low-dose reactivity, would require careful risk management of AAR.