The consistency and influence of environmental and animal factors on exhaled breath condensate hydrogen peroxide, pH and leukotriene B4 in horses

•Exhaled breath condensate (EBC) analysis is a non-invasive method to assess the lower respiratory tract.•Intra- and inter-day consistency for both EBC H2O2 and pH in horses were adequate.•EBC H2O2 was influenced by ambient temperature, humidity, collection location and time of day.•EBC pH was influenced by respiratory rate during EBC collection and ambient temperature.•EBC LTB4 had poor intra- and inter-day consistency. This study was performed to determine the consistency of exhaled breath condensate (EBC) hydrogen peroxide (H2O2), pH and leukotriene B4 (LTB4) measurements in asymptomatic horses and to define the influence of environmental and animal factors on these variables. Intra- and inter-day consistency for both H2O2 and pH measurements were adequate, with intraclass correlation coefficients ≥0.8, whereas the consistency for LTB4 was poor. H2O2 was influenced by ambient temperature (TA), humidity, time of day and collection location (all P