Purpose: The relationship between childhood blood eosinophils and subtypes of allergic diseases remains understudied. This study aimed to examine the associations between childhood blood eosinophils and subtypes of asthma, rhinitis and dermatitis, as well as the modifying effect of age. Methods: We obtained concurrent blood cell counts and serum Immunoglobulin E (IgE) test results in 5026 children (0–13, years) from First Affiliated Hospital of Guangzhou Medical University from 2014 to 2019. Generalized additive models with multivariable adjustments were utilized to model the exposure-response relationship between eosinophils and allergic symptoms. The robustness of the association was assessed in two age categories (<6, 6–13 years). Results: The association of eosinophils with allergic asthma/rhinitis was positively nonlinear, with a plateau at levels of Q (≥0.51, 10/L). Conversely, exposure-response curves between eosinophils and the risk of non-allergic asthma and rhinitis were negatively linear, and especially, became statistically significant when levels of eosinophils were larger than Q (≥0.30, 10/L). Compared with their counterparts, school-aged children (6–13, years) with a higher level of blood eosinophils (≥0.35, 10/L) were more likely to suffer from allergic asthma [relative excess risk due to interaction (RERI), 2.51; 95% CI, 1.24–3.78], allergic rhinitis (RERI, 2.79; 95% CI, 1.14–4.45) but not allergic dermatitis (RERI not significant). Conclusion: Higher eosinophil counts were associated with the increased risk of allergic subtype symptoms and the decreased risk of non-allergic subtypes in children. Moreover, the associations between eosinophils and allergic asthma/rhinitis were accentuated in the school-aged child. These findings may contribute to providing novel insights for clinical administration relevance of allergic-related symptoms.Key messages: There was a positively nonlinear association between childhood eosinophils and allergic asthma/rhinitis. Age modified the associations between eosinophils and allergy-related outcomes. The associations of eosinophil with allergic asthma/rhinitis accentuated in the school-aged child (6–13, years).