Bad breath (also known as halitosis) is a very common problem. It is said to affect nearly 50% of the adult population. There are many different causes. Whether in the form of occasional 'morning breath', which nearly every otherwise healthy adult encounters, or rarer more serious problems, ranging from metabolic disorders to chest tumors.

In up to 90% of the cases the cause for bad breath lies in the mouth. It generally arises as a result of the bacterial decomposition of food particles, cells, blood and some chemical components of saliva. These bacteria are supposed to be there, because they assist humans in digestion. As proteins and other chemicals in these materials are broken down into simpler components, smelly gases are produced. Especially so called volatile sulphur compounds (VSCs) resulting from the bacterial decomposition are responsible for the bad odours.

In addition, bad breath can be caused by the following:

• Poor dental hygiene — infrequent or improper brushing and flossing can leave food particles to rot inside the mouth
• Local infections in the mouth —gum disease
• Respiratory tract infections — throat infections, sinus infections, lung infections
• External agents — garlic, onions, coffee, cigarette smoking, chewing tobacco
• Dry mouth (xerostomia) — this can be caused by salivary gland problems, medications or by "mouth breathing"
• Systemic illnesses — diabetes, liver disease, kidney disease, lung disease, sinus disease, reflux disease and others
• Psychiatric illness — Some people may perceive that they have bad breath, but it is not noticed by oral health care professionals or others. This is referred to as "pseudohalitosis”