Supporting the Th2-promoting activity of TiO2, it was shown that these nanoparticles can potentiate allergic reactions [21,22,23] and that intratracheally instilled TiO2NPs induce an increased number of mast cells (MCs) and increase interleukin 13 (IL13) secretion in the bronchoalveolar lavage (BAL) of treated rats [24]. The gene discussed is IL13; the disease is allergic disease.