The main cause of bad breath is bacteria in the mouth. The mouth and throat are home to aerobic bacteria that are dependent on oxygen to live, along with anaerobic bacteria that do not need oxygen. The aerobic bacteria prevent the proliferation of anaerobic bacteria. However, the right conditions in the mouth and throat can cause anaerobic bacteria to multiply rapidly, leading the aerobic bacteria to withdraw and destroying the natural, healthy balance in the mouth. Anaerobic bacteria primarily feed on leftovers from foods rich in protein, such as meat, fish or dairy products. The more protein that is there for the bacteria to feed on, the more they can multiply. The excretions made by the anaerobic bacteria are the cause of bad breath. These volatile sulfur compounds make the breath smell rotten, which is why these bacteria are called putrefying bacteria.
Good dental hygiene prevents the build-up of leftover food in the mouth and puts an end to the ideal conditions for putrefying bacteria to thrive in.