Doctors since ancient times have been able to detect ailments from the smell of a patient’s breath, and the practice is now getting a boost from 21st-century technology, the Wall Street Journal finds. Researchers are identifying thousands of compounds that leave traces in exhaled breath and developing tools that can diagnose and monitor a large number of illnesses by requiring patients to do nothing more than blow into a machine. In some cases, fast, painless, and cheap breath tests can provide more information than blood tests.
