The odor of exhaled gas is caused by many reasons. Clinically, it is more common to have respiratory system diseases, such as chronic pharyngitis, rhinitis, sinusitis, lung abscess caused by infection with bacteria and amoeba in the lung; the cause needs to be clarified and treated accordingly. When the exhaled gas smells like rotten apple, it is common to have diabetic ketoacidosis, so insulin should be used to stabilize blood sugar and correct the disorder of electrolyte and acid-base balance. When the exhaled gas smells like garlic, it is common to have organophosphorus pesticide poisoning, so atropine, desipramine and oxygen should be used in time to ensure normal vital signs.