The aim of this study is to compare the effects of aerobic conditioning (AC) before (ACBS) and after (ACAS) allergic sensitization. BALB/c mice were divided into two main groups: ACBS and ACAS. Each groups was divided into subgroups: control (nonsensitized/nontrained), AC (nonsensitized/trained), ovalbumin (OVA) (sensitized/nontrained), AC+OVA (trained/sensitized), and OVA+AC (sensitized/trained). Sensitization was induced using OVA and AC performed in treadmill (moderate intensity). We examined IgE and IgG1 levels, eosinophil counting, expression of Th1 (interleukin (IL)-2, IFN-α) and Th2 cytokines (IL-4, IL-5, IL-13), IL-10, vascular endothelial growth factor (VEGF), and airway remodeling. IgE and IgG1 were decreased only when exercise was performed before sensitization (ACBS); however, there was a decrease of eosinophils, Th2 cytokines, VEGF, and airway remodeling and increase in IL-10 in either ACBS or ACAS groups. Our results demonstrate that aerobic conditioning reduces Th2 response before and after sensitization by increasing IL-10 while the production of anaphylactic antibodies is reduced only when exercise is performed before sensitization.