Halitosis may be a sign of:

Systemic pathologic changes: intestinal, hepatic, pulmonary, renal, and stomachical chances, diabetes, fever, and so on.

Local pathologic changes: Originated in the mouth: periodontal diseases, cavities, stomatitis, cicatrization of surgical wounds, neoplasia, myiasis, poor mouth hygiene.

Not originated in the mouth: tonsillitis, pharyngitis, sinusitis, adenoids, rhinitis, foreign objects in the nasal fossa, and tonsillar cryptae.

Physiological changes and adaptive processes such as: Halitosis caused by eliminating substances which produce fetid volatile derivatives; strong-smelling food; tabagism; medication.

Halitosis caused by hypoglycemia: low-calorie diet, fasting, long intervals between meals, strenuous physical exercises. Morph tongue hunger, and diet halitosis, dehydration, xerostomia, psychological stress, morphtongue changes, and coated tongue.