What are the causes of halitosis (bad breath)?

Causes of Bad Breath (Halitosis)

The most common causes of halitosis are oral conditions (about 85-90% of cases), particularly tongue coating, periodontal disease, poor oral hygiene, and oral infections. 1, 2

Oral Causes of Halitosis

• Tongue coating: Bacterial accumulation on the posterior third of the dorsal surface of the tongue is the most frequent cause of oral halitosis 3, 4
• Periodontal disease: Active gum disease leads to volatile sulfur compound production 1, 5
• Poor oral hygiene: Inadequate plaque control allows bacterial overgrowth 2
• Dental problems:
  • Deep carious lesions 1
  • Faulty dental restorations 3
  • Ill-fitting dentures 4
  • Food impaction between teeth 5
• Oral infections:
  • Pericoronitis (infection around partially erupted teeth) 1
  • Peri-implant disease 1
  • Mucosal ulcerations 1
• Dry mouth (xerostomia): Reduced saliva flow decreases natural oral cleansing 1

Non-Oral Causes of Halitosis (10-15% of cases)

Respiratory System

• Sinusitis: Halitosis is a recognized symptom of acute bacterial rhinosinusitis 6
• Postnasal drainage: Can cause bad breath, especially with chronic rhinitis 6
• Tonsil infections: Throat infections can contribute to halitosis 2
• Respiratory tract infections: Both upper and lower respiratory infections 3

Gastrointestinal System

• Acid reflux/regurgitation: Can contribute to oral malodor 3

Systemic Conditions

• Liver disease: Hepatic insufficiency 3
• Kidney disease: Renal insufficiency can cause salivary disorders affecting breath 7, 3
• Metabolic disorders: Including diabetes 2
• Trimethylaminuria: A rare genetic disorder causing fish-like odor 3, 2

Other Contributing Factors

• Certain foods: Particularly those containing volatile compounds (e.g., garlic, onions) 1
• Tobacco products: Smoking causes distinctive breath odor 1
• Medications: Some medications can cause dry mouth or directly affect breath odor 1
• Alcohol consumption: Moderate to heavy use 6

Pathophysiology

• Volatile Sulfur Compounds (VSCs): The primary cause of bad breath is bacterial breakdown of proteins resulting in VSCs (hydrogen sulfide, methyl mercaptan, dimethyl sulfide) 1, 3
• Bacterial action: Gram-negative anaerobic bacteria are primarily responsible for producing these compounds 5
• Substrate availability: Presence of protein-rich substrates (food debris, blood, dead cells) increases VSC production 1

Diagnostic Considerations

• Differential diagnosis: It's crucial to distinguish between oral and non-oral causes of halitosis 4
• Self-perception: Some patients complain of halitosis when no measurable bad breath exists (pseudohalitosis) 5
• Assessment methods:
  • Organoleptic testing (human sense of smell) 3
  • Sulfide monitoring devices 3
  • Gas chromatography for more precise analysis 3

Common Pitfalls in Diagnosis and Management

• Overlooking tongue coating: Many practitioners focus only on periodontal disease and miss the most common cause 4
• Misattributing to gastrointestinal causes: While popular belief associates bad breath with stomach problems, true gastrointestinal causes are relatively uncommon 5
• Inadequate assessment: Failure to perform comprehensive evaluation may miss non-oral causes 5
• Overreliance on mouthwash: Temporary masking without addressing underlying causes 4

Understanding the multifactorial nature of halitosis is essential for proper diagnosis and effective management. Most cases can be successfully treated by addressing oral hygiene, particularly tongue cleaning, and treating any underlying oral conditions.