Background Evidence suggests a causal relationship between obesity and asthma; however, the underlying mechanisms remain unknown.Substance P (SP), involved in neurogenic inflammation by acting through its receptor NK1-R, seems to participate in obeseasthma phenotype in mice.Objectives To evaluate the effect of a selective substance P receptor antagonist on a mouse model of diet-induced obesity and asthma.MethodsDiet-induced obese Balb/c mice were sensitized and challenged with ovalbumin (OVA) and treated with a selective NK1-Rantagonist or placebo. Serum glucose, insulin, IL-6, resistin, and OVA-specific IgE levels were quantified. A score for peribronchial inflammation in lung histology was used. Cells were counted in bronchoalveolar lavage fluid. Adipocyte sizes were measured.Results Ovalbumin-obese mice treated with NK1-R antagonist had lower weight (P = 0.0002), reduced daily food intake (P = 0.0021),reduced daily energy intake (P = 0.0021), reduced surface adipocyte areas (P < 0.0001), lower serum glucose (P = 0.04), lowerserum insulin (P = 0.03), lower serum IL-(P = 0.0022), lower serum resistin (P = 0.0043), lower serum OVA specific IgE (P =0.035), and lower peribronchial inflammation score (P < 0.0001) than nontreated OVA-obese mice. We observed an interaction between obesity, allergen sensitization, and treatment with NK1-R antagonist for metabolic and systemic biomarkers, and forallergen sensitization and bronchial inflammation, showing a synergy between these variables.Conclusion & Clinical Relevance In an experimental model of obesity and asthma in mice, NK1-R blockade improved metabolic and systemic biomarkers, as wellas allergen sensitization and bronchial inflammation. These positive effects support a common pathway in the obese–asthma phenotype and highlight SP as a target with potential clinical interest in the obese–asthma epidemics. Background Evidence suggests a causal relationship between obesity and asthma; however, the underlying mechanisms remain unknown. Substance P (SP), involved in neurogenic inflammation by acting through its receptor NK1-R, seems to participate in obese asthma phenotype in mice. Objectives To evaluate the effect of a selective substance P receptor antagonist on a mouse model of diet-induced obesity and asthma. Methods Diet-induced obese Balb / c mice were sensitized and challenged with ovalbumin (OVA) and treated with a selective NK1-Rantagonist or placebo. Serum A score for peribronchial inflammation in lung histology was used. Cells were counted in bronchoalveolar lavage fluid. Adipocyte sizes were measured. Results Ovalbumin-obese mice treated with NK1-R antagonist had lower weight (P = 0.0002), reduced daily food intake (P = 0.0021), reduced daily energy intake (P = 0.0021), reduced surface adipocyte areas 001), lower serum glucose (P = 0.04), lowererserum insulin (P = 0.03), lower serum IL- (P = 0.0022), lower serum resistin We observed an interaction between obesity, allergen sensitization, and treatment with NK1-R antagonist for metabolic and systemic biomarkers, and forallergen sensitization and bronchial inflammation, showing a synergy between these variables. Confocal & Clinical Relevance In an experimental model of obesity and asthma in mice, NK1-R blockade improved metabolic and systemic biomarkers, as wellas allergen sensitization and bronchial inflammation. These positive effects support a common pathway in the obese-asthma phenotype and highlight SP as a target with potential clinical interest in the obese-asthma epidemics.