Halitosis (bad breath) can be occasional or chronic, and can persist despite good oral and dental hygiene.
Certain hormonal changes, medical problems or drugs can affect breath odor. However, the most common causes are mouth-related: bad hygiene, dental problems (e.g. dental caries(tooth decay), abscesses or gum diseases), mouth breathing, smoking, some foods,etc.
Good daily oral hygiene, a healthy lifestyle and regular visits to your dentist for professional cleaning and care eliminates most causes of halitosis.