Actually talking each humanbeings are badbreathres. Oral cavity contains millions of anaerobic bacteria like fusobacterium as well as actinomyces which functions on the protein of food supplies and putrifies them. This procedure results in the development of offenssive gases like hydrogen sulphide,methyl mescaptan,cadaverin,skatol,putrescine etc producing bad smell. If oral hygiene isn't maintained properly all will suffer from bad breath. A lot of us control this by regular brushing,tongue cleaning and gargling. Even with maintining cleanliness in the mouth some people suffer from offenssive smell because of numerous causes which must be diagnosed as well as taken care of properly.
Some frequent causes of bad breath.

1) Poor oral hygiene:
When oral hygiene isn't maintained properly the mouth gets the seat for countless bacteria which produce offenssive gases by degrading the food debris. Bad breath is acute in those who do not brush their teeth regularly and clean their mouth after every food. Snacks taken between meals can also produce bad breath after tooth extraction (www.sequimgazette.com) breath because of improper cleaning.
Badbreath is prevalent in almost all people in the morning on waking. During rest there's much less production of saliva.Saliva seems to have some antibacterial properties which help to preserve the mouth fresh. Saliva conains oxygen molecules that is called for to make oral cavity cardiovascular. Therefore the decrease in it's quantity during rest can make a favourable condition for anaerobic bacteria.

Two) Food habits:
The principle cause of bad smell can be due to degradation of protein by the bacteria and hence just about all food products rich in protein favours bad breath. Meat,fish,milk products, etc and eggs,cakes,nuts,pear can cause bad breath. Several food articles are able to make certain type of smell which may be unpleasent. Raw onion is able to produce normal bad smell. It's said that an apple one day keeps the surgeon away,a raw onion a day keeps everybody at bay. Eating groundnuts can also produce bad smell. However if appropriate cleaning is done smell could be reduced irrespective of the nature of food. Irregularity in timing of meals may also produce bad breath. Little food articles taken in between the meals can also take bad smell.

Three) Biofilm:
There is formation of a thin gluey coating known as biofilm on the tongue as well as oral mucosa. This covering is thick on the posterior feature of the tongue where numerous gram damaging bacteriae are noticed.The thick coating on the tongue is always linked with badbreath. Even a thin biofilm is able to create anaerobic state favourable for bacterial proliferation.