In vivo, CRTH2 mediates mobilization of eosinophils from guinea-pig bone marrow [17], promotes eosinophilia and exacerbates pathology in mouse models of allergic asthma and atopic dermatitis [18], and induces eosinophil infiltration into the airways upon intratracheal administration of PGD2 or a selective CRTH2 agonist [19-21]. Here, PTGDR2 is linked to allergic asthma.