Since the time of Hippocrates, physicians have known that the odour of human breath can provide clues to diagnosis.
In the past, hydrogen peroxide which is a marker of inflammatory diseases and oxidative stress was the most
studied substance in the exhaled breath which was detectable in the liquid that obtained by condensing or cooling. The
advantages of breath analysis are that it is convenient, non-invasive, and could be performed with children as well as mechanically
ventilated patients. Today, exhaled nitric oxide has been studied extensively, especially in relation to asthma.
More than a thousand different volatile organic compounds have been observed in low concentrations in normal human
breath. Alkanes and methylalkanes have been increasingly used by physicians as a novel method to diagnose many diseases
without discomforts of invasive procedures. Although the limitations of measurement of exhaled nitric oxide in direct
diagnosis of infectious pulmonary TB, it may have potential development as a cost-effective replacement of chest radiological
examination in screening algorithms. None of the individual exhaled volatile organic compound alone is specific
for disease. Exhaled breath analysis techniques may be available to diagnose and monitor the diseases in home setting
when their sensitivity and specificity are expected to improve in the future. Here, we also discussed some patents related
to the topic.