Asthma is a chronic allergic disease that is often comorbid with anxiety disorders. The hippocampus in the brain is involved in emotion regulation and has a high density of microglia - immune cells that become active during immune responses. In a mouse model, we determined whether asthma symptoms during development led to increased anxiety behavior and microglial activation in the hippocampus using gene expression, and staining. The results support the comorbidity between asthma and anxiety.