The causes of sour odor in the armpit area are divided into physiological and pathological: 1, physiological sour odor is due to prolonged exercise or emotional excitement, high temperature and other factors that lead to a large amount of sweat secretion in the armpit, thus triggering the symptoms. These sweat in the armpits after evaporation will appear obvious sour smell, after appropriate cleaning, the smell will disappear, do not worry too much. 2, pathological sour smell: mainly because of fox odor, triggered by underarm sweat glands secrete a lot of sweat, thus triggering the bad smell, is a genetic factor triggered by the symptoms, can be around the onset of puberty. And sour smell may also be due to local infection fungus triggered by armpit hair ringworm, fungus in the process of decomposition and metabolism will produce sour smell, and will stimulate the itching of the underarm skin, and in the armpit hair area residual white or yellow slimy material.