An exhaled breath nitric oxide measurement of 42 (in ppb) is not normal and usually indicates the presence of inflammation within the airways. Exhaled nitric oxide is produced by airway epithelial cells in the body’s lungs, and the concentration of nitric oxide is closely associated with airway inflammation. In the clinic nitric oxide below 25 ppb in adults is a normal presentation, while nitric oxide exhaled breath measurement of 42 ppb is higher than normal, so it is not a normal condition. Nitric oxide in exhaled breath is often higher than normal, suggesting that the number of eosinophils in the airway is elevated, i.e., there is inflammation in the airway, which is mostly seen in allergic diseases such as bronchial asthma and eosinophilic bronchitis; in addition, chronic obstructive pulmonary disease and chronic bronchitis can also cause increased nitric oxide values. There are other reasons that can also cause an increase in the nitric oxide value of exhaled breath. If you find an increase in the nitric oxide value, it is recommended that you go to the hospital as soon as possible, complete the examination, make a clear diagnosis, and standardize the treatment under the guidance of the doctor.