AHR and asthma: investigated the effect of CuO NP exposure by intranasal instillationduring OVA challenge phases and they found that CuO NP aggravatedthe development of asthma by enhancing AHR.12 Mice exposed to TiO2 NPs during OVA sensitization showeda decrease in AHR and eosinophilia, while exposure of TiO2 NPs during the challenge phase enhanced the airway inflammationand caused loss in body weight.33