Interestingly, prenatal exposure to maternal cigarette smoke has been linked to the abnormal DNA methylation status of the 5′-CpG-island in the thymic stromal lymphopoietin (TSLP [81]), a key immune cytokine gene involved in the pathogenesis of asthma [82,83], atopic dermatitis [84], and pediatric eosinophilic esophagitis [85]. Here, TSLP is linked to asthma.