A previous study showed that in utero exposures of C57BL/6 mice to 50mg/m3 of cigarette smoke led to exacerbated HDM-induced asthma in terms of increases in airway resistance, eosinophilic inflammation, and Il-4, Il-5, and IgE levels when compared to filtered-air controls (Eyring et al., 2015). Here, IL4 is linked to asthma.