Bacteria: Food particles left in your mouth after a meal combine with bacteria to create a bad odor. Bacteria often collects on the back of your tongue.
Gum Disease: Gum disease is an infection of the gums. The infection can also cause bad breath.
Dry mouth: Saliva cleanses your mouth, washing away many odor-causing bacteria. A dry mouth means too little saliva. This can lead to bad breath. Your mouth may become dry when you sleep, if you don't drink enough fluids, or because of certain medications.
Certain foods: Some types of food and drink can cause bad breath. These include garlic, onions, fish, cabbage, coffee and alcohol.
Tobacco: Smoking or chewing tobacco can make your breath smell. This bad breath stays with you even when you're not smoking or chewing.
Appliances: Braces, dentures and other mouth appliances may cause bad breath if not kept clean.
Medical Problems: Certain medical problems may cause bad breath like drainage from sinus, diabetes, and some respiratory and gastrointestinal problems. Bad breath becomes more of a problem as you age.
Brush your tongue: Brush your tongue (or use special tongue scraper) to clean off food and odor causing bacteria. Brush as far back as you can.
Keep a moist mouth: Drink plenty of water and rinse your mouth with water every so often to keep saliva flowing. Chewing sugarless gum can also help.
Make diet changes: Try to avoid foods that can cause bad smelling breath.
Stop Smoking: If you smoke or chew tobacco, quit. You'll be amazed how much better your breath will smell.
Ask about mouth rinses: Most over the counter mouthwashes only cover up bad breath for a short time. However, your dentist may suggest a prescription mouth rinse that can help kill odor causing bacteria.