The purpose of this study is to determine mean or median of fractional exhaled nitric oxide (FeNO) in Thai atopic asthmatic children that divided into subgroups due to asthma exacerbation according to the global initiative for asthma guideline.

From many previous studies, fractional exhaled nitric oxide (FeNO) has many benefits such as non-invasive, easily to perform, less time consume, has direct association with severity of inflammation of bronchial trees and sputum eosinophils, has benefit for diagnosis and monitoring the treatment in asthmatic patients.

In Thailand, this field of study is less extend, especially in children population. The investigators hypothesized that patients with asthma exacerbation may have high level of fractional exhaled nitric oxide (FeNO) than non exacerbation group.

It is therefore desirable to examine the association between fractional exhaled nitric oxide (FeNO) and asthma exacerbation among atopic asthmatic Thai children and will be the main objective of this research.

Inclusion Criteria:

• clinical diagnosis of atopic bronchial asthma follow up in clinic of allergy and clinical immunology, Siriraj hospital

Exclusion Criteria:

• smoker or past history of smoking
• chronic disease eg. HIV infection, pulmonary hypertension, systemic lupus erythematosus, liver cirrhosis, gastroesophageal reflux, COPD, bronchiectasis
• drink ethanol within 48 hours before enrollment
• history of upper or lower respiratory tract infection within 6 weeks before enrollment drink caffeine within day before enrollment during pregnancy history of systemic steroid use within 8 weeks before enrollment

atopic asthmatic patients in Department of Pediatrics, Siriraj hospital (tertiary care)