Hello there, Oral malodour or halitosis is mainly due to oral or nasopharyngeal reasons.Nasal obstruction like upper respiratory tract infection causes halitosis. Mostly fowl odour is caused by poor oral hygiene that is accumulation of food debris, dental bacterial plaque on teeth and tongue which leads to gingival (gum) and periodontal inflammation. Acute necrotising ulcerative gingivitis is the oral condition that causes most notable halitosis. Maintain good oral hygiene by proper tooth brushing and flossing, keep your tongue clean using tongue cleaners, mouth rinsing with chlorexidine reduces mal odour. avoid spicy food stuffs in your dietn,visit a dentist and go for oral prophylaxis. i hope that helps you.