Bad breath causes1
The breakdown of food particles stuck in your teeth can increase bacteria and cause a bad smell. Also, certain foods like onions and garlic can lead to bad breath. Once digested, they enter your bloodstream, get carried to your lungs and you breathe out the foul smell.
Poor dental hygiene
Brushing and flossing give you more than a nice smile—they clean away food particles that can cause mouth odor. If left in your teeth, these particles can eventually cause gum disease and more bad breath. Odor-causing bacteria can also collect on top of and underneath your tongue, so you should clean your tongue as well.
Saliva helps cleanse your mouth of food particles that can cause bad breath over time. A condition called dry mouth, or xerostomia, happens when the salivary glands in your mouth don’t make enough saliva to keep your mouth wet. With less salvia, your chances of bad breath increase.
Certain medications can give you dry mouth that leads to mouth odor. Also, some drugs can cause bad breath once they’re broken down in your body (just like onions and garlic).
Smoking cigarettes causes its own bad mouth odor, and smokeless/chewing tobacco can do the same. Even worse, any type of tobacco use can lead to more serious oral health issues like gum disease, receding gums, bone loss and tooth loss.
Poor digestion, constipation and bowel disorders can all cause an unpleasant mouth odor. Acid reflux, also known as gastroesophageal reflux disease, or GERD, can produce a breath odor as well.