IGHE and allergic asthma: In mouse models of allergic asthma, the absence of microbial colonization (by maintenance in germ-free conditions or by administration of antibiotics early in life) increases total IgE and T2-associated cytokines in BAL, airway eosinophilia, and airway resistance (Herbst et al., 2011; Olszak et al., 2012; Russell et al., 2012).