The Future of Hydrogen Peroxide as a Biomarker for Airway Inflammation

Abstract: Airway inflammation has traditionally been assessed using invasive or semi-invasive techniques, prompting growing interest in non-invasive biomarkers. Exhaled breath condensate (EBC) offers a repeatable and well-tolerated method to evaluate airway inflammation and oxidative stress, with hydrogen peroxide (H 2 O 2 ) emerging as a biomarker with relevant translational potential for disease monitoring and treatment response. This narrative review aimed to evaluate the potential H 2 O 2 in EBC as a non-invasive biomarker for disease monitoring and treatment response in inflammatory respiratory diseases. Key clinical studies investigating H 2 O 2 in patients with asthma, COPD, bronchiectasis and acute lung conditions were analyzed. Exhaled H 2 O 2 levels are elevated in several inflammatory respiratory diseases, reflecting airway oxidative stress and disease instability, with higher concentrations observed in untreated or exacerbated patients, which decline in response to therapy. These findings indicate that H 2 O 2 appears to be a promising tool for assessing airway oxidative stress and inflammation. Further research is needed to validate its clinical relevance and support its integration into standard clinical management. Keywords: exhaled breath, diagnosis, disease monitoring, respiratory diseases, clinical practice