Asthma is one of the most common chronic disease worldwide, imposing a substantial social burden on both children and adults.

What needs to be kept in mind, especially in assessing treatment effect of allergic inflammation in children with asthma, is that symptom score and spirometry measures have limitations, mainly their subjectivity (symptom scores), wide variability, and lack of stability in short time period (symptom scores and spirometry measures).

Monitoring allergic inflammation in the course of asthma in children with exhaled nitric oxide measurement (FeNO) may allow to titrate the dose of inhaled glucocorticosteroids more precisely, depending on individual patients requirements.

The aim of this study is to assess the utility of FeNO in treatment monitoring in children with asthma.

According to the aim of the study following assumptions are formulated:

1. Comparison of annual cumulative steroid dose, number of bronchodilator doses taken, number of asthma exacerbation, number of hospitalisation due to asthma, between group of children with asthma with FeNO monitored treatment (study group), and group of children with treatment monitored by GINA's grade of disease clinical control (control group)
2. Assessment of corelation of FeNO (ppb) with symptom score (points)and lung function (FEV1)
3. Comparison of values of non-specific bronchial hyperresponsiveness with methacholine (PC20M)between both study groups after 12. months of treatment.