The Future of Hydrogen Peroxide as a Biomarker for Airway Inflammation

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 (H₂O₂) emerging as a biomarker with relevant translational potential for disease monitoring and treatment response. This narrative review aimed to evaluate the potential H₂O₂ in EBC as a non-invasive biomarker for disease monitoring and treatment response in inflammatory respiratory diseases. Key clinical studies investigating H₂O₂ in patients with asthma, COPD, bronchiectasis and acute lung conditions were analyzed. Exhaled H₂O₂ 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 H₂O₂ 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.