What could be causing me to breathe through my mouth instead of my nose?

Mouth Breathing: Causes and Clinical Approach

Mouth breathing instead of nasal breathing is most commonly caused by nasal obstruction from conditions like allergic rhinitis, nasal polyps, adenoidal hypertrophy (especially in children), or anatomical abnormalities—and requires systematic evaluation to identify the underlying cause and prevent complications. 1

Primary Causes by Age Group

In Adults

• Allergic rhinitis is the most frequent cause, presenting with nasal congestion, itching, sneezing, and runny nose that forces mouth breathing 2
• Chronic rhinosinusitis with nasal polyps causes bilateral obstruction and is associated with significantly lower nasal nitric oxide levels due to sinus ostial blockage 1
• Anatomical abnormalities including deviated nasal septum, turbinate hypertrophy, or nasal valve collapse can create mechanical obstruction 1
• Nonallergic rhinitis from vasomotor dysfunction, medications, or hormonal changes may cause persistent nasal congestion 1

In Children and Infants

• Adenoidal hypertrophy is the most common acquired cause of nasal obstruction in children, typically presenting with mouth breathing, nasal speech, and snoring 1
• Infants below 2-6 months are obligate nasal breathers, so even minor nasal congestion from upper respiratory infections can force mouth breathing and potentially cause life-threatening airway obstruction 1
• Laryngopharyngeal reflux in infants causes inflammation and narrowing of the posterior choanae, leading to nasal obstruction, frequent choking, and mouth breathing 1

Serious Conditions Requiring Urgent Evaluation

Red Flag Presentations

• Primary ciliary dyskinesia (PCD) should be suspected when chronic nasal obstruction is accompanied by recurrent sinopulmonary infections, with nasal nitric oxide testing showing values below 77 ppb being highly suggestive 1
• Cystic fibrosis presents with low nasal nitric oxide (70-300 ppb) and chronic rhinosinusitis, requiring sweat chloride testing for diagnosis 1
• Unilateral nasal obstruction with bleeding raises concern for malignancy, particularly in patients with occupational exposure to nickel or chrome 1
• Cerebrospinal fluid rhinorrhea presents as refractory clear rhinorrhea and may occur spontaneously in middle-aged women with benign intracranial hypertension 1

Diagnostic Approach

Initial Assessment

• Document the duration, laterality (unilateral vs bilateral), and progression of symptoms 1
• Identify associated symptoms: sneezing, itching, and clear rhinorrhea suggest allergic rhinitis; purulent discharge suggests infection; bleeding suggests trauma or malignancy 1, 2
• Perform anterior rhinoscopy to visualize nasal mucosa, turbinates, septum, and presence of polyps or masses 1
• In children, assess for adenoidal facies (open mouth posture, elongated face) and inquire about snoring or sleep disturbance 1

Specialized Testing When Indicated

• Nasal nitric oxide measurement is a sensitive and specific test for PCD in cooperative patients, with values below 77 ppb being very suggestive when cystic fibrosis is ruled out 1
• Allergy testing (skin prick or specific IgE) should be performed when allergic rhinitis is suspected based on symptoms of sneezing, itching, and clear rhinorrhea 1
• Videofluoroscopic swallow study or flexible endoscopic evaluation should be considered when dysphagia or aspiration is suspected as contributing to respiratory symptoms 1

Management Based on Etiology

For Allergic Rhinitis

• Intranasal corticosteroids (such as fluticasone propionate 200 mcg once daily in adults, 100 mcg once daily in children ≥4 years) are first-line treatment, with effects beginning within 12 hours but reaching maximum benefit after several days of regular use 2
• Avoid allergen exposure when possible and consider adding oral antihistamines for breakthrough symptoms 2
• Monitor for adverse effects including epistaxis (6.9%), nasal burning (3.2%), and rarely nasal septal perforation with prolonged use 2

For Structural Abnormalities

• Adenoidectomy is indicated for children with sleep apnea from adeno-tonsillar hypertrophy, chronic adenoiditis, or chronic sinusitis causing persistent mouth breathing 1
• Surgical correction of deviated septum or turbinate reduction may be necessary for anatomical obstruction not responsive to medical therapy 1

For Laryngopharyngeal Reflux in Infants

• Thickened feedings, upright positioning after feeding, and histamine-2 receptor antagonists or proton pump inhibitors are the mainstay of treatment 1
• Be aware that gastric acidity inhibitors may increase risk of acute gastroenteritis and community-acquired pneumonia 1

Critical Complications to Prevent

• In neonates, complete or partial nasal obstruction can lead to fatal airway obstruction since many are obligate nasal breathers, with nasal passages contributing up to 50% of total airway resistance 1
• Chronic mouth breathing can lead to dental malocclusion, altered facial development in children, and increased risk of upper respiratory infections 1
• Aspiration risk increases when protective laryngeal reflexes are compromised by chronic upper airway inflammation or anatomical abnormalities 1