There are a number of different causes of bad breath which are outlined below:

Poor dental hygiene

The most common cause of bad breath (90% of cases) is poor dental hygiene. Naturally occurring bacteria in your mouth breaks down food particles and proteins. As the bacteria breaks down the food and proteins, a smelly gas is released. Sometimes, food that is trapped between your teeth can rot and contain bacteria, causing bad breath. However, regular brushing and flossing will help prevent this.

Bad breath can also be caused if you have plaque on your teeth, or gum disease. Plaque is a soft, white deposit that forms on the surface of the teeth when bacteria combine with food and saliva. Gum disease varies in severity from mild to severe, and involves the tissues surrounding your teeth becoming inflamed or infected.

Occasionally, some people develop a bacterial coating on the back of their tongue, and this can cause bad breath.

Morning bad breath

Most people find that their breath smells bad after waking up in the morning. This is normal and occurs because the mouth dries up overnight, and the flow of saliva that washes away food particles slows down when we are asleep. Bacteria quickly break down any food residue, in the mouth, and an unpleasant, stale smell is released. However, the flow of saliva usually increases once you start eating.

Food and drink

Strongly flavoured foods, such as garlic, onion and spices often cause your breath to smell after you have eaten food containing them. Strong smelling drinks, such as alcohol and coffee, can also cause bad breath. However, this type of bad breath is usually temporary and can be easily avoided by not eating or drinking these foods or drinks.

Medicines

Sometimes, certain medications can cause bad breath. You should discuss possible alternatives with your doctor.

Smoking

If you smoke, your breath is likely to smell of stale smoke. Smoking also increases your risk of getting gum disease, which is another cause of bad breath. Stopping smoking will lower this risk and prevent smoke-related bad breath.

Medical causes

Medical causes of bad breath are rare (about 10%), but they can occur. If you have a throat or tonsil infection, the catarrh that is produced can cause bad breath. Other conditions that may also cause bad breath include:

• dry mouth (xerostomia) - a condition that affects the flow of saliva and leads to a build up of bacteria in the mouth,
• infections of the throat, nose and lungs such as bronchitis or sinusitis,
• diabetes,
• liver or kidney problems,
• gastritis and food reflux, and
• low carbohydrate diets, such as the Atkins diet.