Halitosis / Bad Breath :

Foul smelling breath affects millions of people and there is a thriving industry providing products to combat halitosis. 
Strict oral hygiene and natural remedies usually provide relief but if bad breath persists, careful dental or medical detection can often reveal an underlying cause.

Causes of halitosis :

Bad breath, or halitosis, can often be traced back to the effects of eating highly spiced foods such curries and garlic or onions, smoking, or drinking alcohol. It is caused by the odour-causing bacteria in the mouth and the drier your mouth, the more bacteria thrive.
Dryness in the mouth is often the result of breathing through the mouth, crash diets (the less food you chew the less saliva is produced), certain drugs and advancing age. 

Bad breath is often more common in the morning because salivation is suppressed whilst sleeping; bacteria collects on the tongue and in food debris that is caught in the teeth, especially when cavities are present.  Persistent halitosis / bad breath can also be caused by gum disease or a chronic sinus infection and irregular bowel habits, digestive problems or constipation.

Remedies for bad breath / halitosis :

Natural strategies for bad breath work best when included in regular and thorough oral hygiene including cleaning the teeth and tongue, and flossing. 
A drop of peppermint oil on the tongue can be very efficacious, as apart from its taste and aroma, it is effective in killing bacteria.  Drinking peppermint or spearmint teas as well as plenty of water will also help to fight bad breath. Clean your teeth after every meal and floss once a day and use a tongue scraper to take coating on the back of the tongue.  Avoid strong-smelling foods and alcohol and do not smoke. 
Also, the phytochemicals in citrus fruit help to normalise bowel flora so try to eat an orange daily. Various food supplements such as probiotics, caprylic acid and citrus extract are most helpful.

If, despite these measures, bad breath persists your doctor or dentist can check for any underlying medical cause.

Information page on halitosis | bad breath.