Bad breath is also called halitosis. The unpleasant smell in the mouth can occur from time to time, or it can be long lasting, depending on the cause.

The primary cause of bad breath in many people is bacteria. Millions of bacteria live in the mouth, particularly on the back of the tongue. The mouth's warm, moist conditions are ideal for the growth of these bacteria.

1) Brush your tongue at least twice a day: Brush your tongue – especially the back of the tongue –while brush your teeth. Volunteers reduced their perception of bad breath by 70% by brushing the tongue, one study found.

2) Floss: Flossing helps removes plaque, a coating of bacteria that forms around the tooth that causes bad breath.

3) Gargle with peroxide: Gargling with an antimicrobial mouthwash is recommended.

4) Use fluoride mouth rinse: Fluorides can prevent tooth decay that causes bad breath.

5) Drink plenty of water: Lack of fluids can lead to dry mouth (xerostomia) and cause bad breath, experts say.

Some types of bad breath, however, are considered to be normal. One example is "morning mouth." This occurs because of the changes in your mouth while you sleep.

During the day, saliva washes away decaying food and odors. The body makes less saliva at night. Your mouth becomes dry, and dead cells stick to your tongue and to the inside of your cheeks. When bacteria use these cells for food, they produce a foul odor.