The first direct evidence on regulatory effects of oral pathogens on allergic airway inflammation and responsiveness was reported by Card et al. Their study underlined the temporal importance of the establishment of infection since P. gingivalis infection established before ovalbumin (OVA) sensitization reduced airway levels of Th2 cytokines (IL-4, IL-5, IL-13) and granulocyte-macrophage colony-stimulating factor, and decreased histological inflammation, without the alteration of serum levels of OVA-specific immunoglobulin E (IgE) and airway responsiveness. Here, IGHE is linked to infection.