Halitosis is the proper term for bad breath which occurs in 25% of the population and is caused by over active bacteria in the mouth particularly on the tongue. In some cases they can be over stimulated in certain individuals for reasons such as poor oral health, medication, health conditions, smoking, diet and underlying infection. If larger amounts of bacteria are being produced and not effectively being removed, they produce volatile sulphur compounds which in turn cause bad breath.
If the cause of halitosis is bacteria in the mouth not being removed effectively, attending regular professional cleans will allow the hygienist or dentist to assess which areas in the mouth are accumulating more plaque and demonstrate effective flossing and brushing techniques to reduce the bacterial colonies which may produce sulphur.
In severe cases halitosis can result in social anxiety, so if symptoms persist always see your medical practitioner as halitosis can also be an indication of other health issues eg. acid reflux, post nasal discharge or xerostomia(dry mouth).