The immune response plays an important role in the development of allergic diseases. It is established that a complex network of various immunocytes such as Th2, non-Th2 (Th17), and regulatory T (Treg) participate in allergic reactions. In this study, we examined the frequencies of Th17 cells (IL-17-positive cells) and Treg cells (FOXP3-positive cells) in the peripheral blood and elucidated their participation in pediatric allergic diseases such as bronchial asthma and food allergies. Our study included 35 subjects, 27 with allergic diseases (19 with asthma and 8 with food allergies) and 8 were controls (without any allergic diseases); their age ranged from 1 to 13 years. The frequency of Th17 cells (IL-17-positive cells) among the CD4⁺T cells in the peripheral blood was 2.33±1.29% in patients with bronchial asthma, 1.53±1.34% in those with food allergies, and 1.50±0.809% in controls. These results indicated that only the patients with bronchial asthma had a trend towards a higher frequency of Th17 cells ( p =0.1558). The ratio of Th17 cells to Treg cells did not show any statistical correlation among the patients with bronchial asthma. However, when we excluded the patients with a severe type of asthma, we could obtain an inverse trend between the ratio of Th17 cells to Treg cells ( p =0.1655). This study suggested that Th17 cells and Treg cells participate in pediatric allergic reactions such as bronchial asthma.