H2AX and allergic disease: To gain insight into how short telomeres protect from HDM‐induced allergy, we investigated the impact of Tert deficiency on DNA damage, senescence, and proliferation of Club cells by performing double immunostainings with H2AX (marker of DNA damage), p21 (marker of senescence) and Ki67 (marker of proliferation) in combination with the Club cell marker SCGB1A1 (Figure 4a‐d).