Background Atopy is a genetically determined condition and some atopic people develop airway hyperresponsiveness and sometimes asthma later in life. Since airway inflammation may be present before the onset of clinical symptoms of asthma, early and noninvasive detection of inflammation would be useful in atopic subjects. Mediators produced by activated inflammatory cells may lead to induction of inducible nitric oxide synthase producing nitric oxide (NO) and inducible heme oxygenase releasing carbon monoxide (CO) in the airways. Both monoxides are present in exhaled air and their levels are elevated in asthma reflecting airway inflammation. Objective We have measured exhaled NO and CO levels in atopic and nonatopic healthy non‐smoking subjects to determine whether inflammation is present in the airways. Methods Exhaled NO was measured by a chemiluminescence analyser and exhaled CO electrochemically and NO in asymptomatic atopic and age‐matched nonatopic normal subjects. Results Exhaled NO and CO levels were both significantly elevated in 15 atopic subjects compared with 40 nonatopic individuals (means ± sem : 18.3 ± 3.0 p.p.b. vs 6.3 ± 0.3 p.p.b., P < 0.0001 and 4.7 ± 0.3 p.p.m. vs 2.8 ± 0.2 p.p.m., P = 0.0005, respectively). Conclusion Increase in exhaled monoxide levels may be an early and noninvasive marker of airway inflammation in asymptomatic atopic subjects.
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