What are the common causes of halitosis?

Common Causes of Halitosis

The vast majority (80-90%) of halitosis originates from oral sources, primarily poor oral hygiene, periodontal disease, and bacterial coating on the posterior tongue, while only 10-20% stems from systemic conditions. 1, 2, 3

Primary Oral Causes (80-90% of Cases)

The mouth is the predominant source of bad breath through bacterial production of volatile sulfur compounds:

• Poor oral hygiene and inadequate plaque control lead to bacterial proliferation that generates malodorous compounds 2, 4
• Periodontal disease (gingivitis and periodontitis) creates pockets where anaerobic bacteria thrive and produce sulfur compounds 1, 5, 4
• Tongue coating, particularly on the posterior third of the dorsal tongue surface, harbors excessive bacterial growth that is the single most common oral source 2, 4
• Dental caries and faulty restorations trap food debris and bacteria 3, 4
• Dry mouth (xerostomia) eliminates the natural cleansing mechanism of saliva, allowing unchecked bacterial proliferation 1

Non-Oral/Systemic Causes (10-20% of Cases)

When oral sources are excluded, consider these extraoral etiologies:

Ear-Nose-Throat Conditions (~10%)

• Acute bacterial rhinosinusitis produces halitosis through bacterial infection and purulent postnasal drainage 1, 6
• Chronic rhinitis with postnasal drainage causes malodor when nasal discharge accumulates in the oropharynx 1
• Tonsillitis contributes to bad breath and is a common indication for tonsillectomy in children 1

Gastrointestinal and Systemic Disorders (~5%)

• Renal insufficiency or failure causes uremic compounds to appear in saliva, creating characteristic breath odor 1, 5
• Hepatic failure produces distinct fetor hepaticus 5
• Diabetic ketoacidosis generates fruity acetone breath 5
• Respiratory tract infections (upper or lower) can cause malodor 2, 5

Lifestyle and Dietary Factors

• Moderate to heavy alcohol consumption contributes to halitosis 1
• Tobacco smoking is a recognized cause 3
• Poor diet and certain medications can generate bad breath 2, 3

Clinical Evaluation Approach

When evaluating halitosis, follow this systematic assessment:

First, examine for oral sources:

• Look for signs of periodontal disease including gingival inflammation and pocket formation 1
• Assess tongue coating, particularly the posterior dorsal surface 2, 4
• Identify dental caries, faulty restorations, and oral hygiene status 3, 4
• Evaluate for xerostomia and reduced salivary flow 1

If oral examination is normal, evaluate for systemic causes:

• Check for nasal discharge, postnasal drip, and oropharyngeal cobblestoning suggesting rhinosinusitis 1
• Examine for tonsillar hypertrophy and pharyngeal erythema 1
• Elicit associated symptoms including chronic throat clearing, acid reflux, heartburn, or waterbrash suggesting GERD 1
• Screen for systemic symptoms such as fever, weight loss, or night sweats suggesting serious underlying disease 1

Management Priorities

For oral causes (the majority):

• Establish rigorous plaque control and oral hygiene practices 4
• Treat active periodontal disease definitively 4
• Institute routine tongue cleaning, focusing on the posterior dorsal surface 2, 4
• Ensure adequate hydration and salivary flow, especially in xerostomia cases 1

For non-oral causes:

• Treat underlying sinusitis with antibiotics if bacterial infection persists >10 days, is severe, or demonstrates "double sickening" pattern 6
• Address systemic conditions such as renal insufficiency, hepatic failure, or diabetic acidosis through appropriate medical management 5

Critical Pitfalls to Avoid

The most important clinical error is failing to recognize that genuine halitosis patients often do not notice their own bad breath (the "bad breath paradox"), while conversely, some patients complain of halitosis when none exists (pseudohalitosis or halitophobia) 7. Always perform objective assessment rather than relying solely on patient perception 3, 7.