To cite this article: Celik M, Tuncer A, Soyer OU, Sackesen C, Tanju Besler H, Kalayci O. Oxidative stress in the airways of children with asthma and allergic rhinitis. Pediatric Allergy Immunology 2012: 23: 556561. Abstract Introduction: Even though it is well known that oxidant stress plays an important role in the pathogenesis of asthma, less is known about allergic rhinitis. Moreover, it is not known whether the co-existence of the two diseases augments the level of oxidant stress within a united airway concept. Aim: To define the level of oxidative stress in children with asthma and/or allergic rhinitis in nasal and oral exhaled breath condensates (EBC) of children. Method: Children aged 618 years with asthma (n = 28), allergic rhinitis (n = 17), asthma and allergic rhinitis (n = 100), and healthy controls (n = 74) were enrolled in the study. Levels of malondialdehyde (MDA) as a marker of oxidative stress and reduced glutathione (GSH) as an antioxidant were measured by High-Performance Liquid Chromatography in the EBC. Results: Malondialdehyde levels were higher, and GSH levels were lower in all patient groups compared to healthy controls in both nasal and oral EBC samples (p < 0.01) but there were no differences among the different patient groups. Interestingly, oral MDA levels were lower in patients with asthma and allergic rhinitis [17.78 nm (11.62-23.94)] compared to patients with asthma only [25.71 nm (18.81-32.61)] (p < 0.01). Discussion: Both asthma and allergic rhinitis are associated with increased oxidative stress in the airways in children. However, the co-existence of the two diseases does not augment the oxidant stress further.