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Nasal Physiology and the Role of Mucus
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The nasal cavity serves multiple physiological functions beyond respiration:
- Airflow Conduction – It provides a conduit for inspired air.
- Air Conditioning – The mucosa warms and humidifies the air via an extensive vascular network.
- Filtration – Cilia, mucus, and nasal hairs trap inhaled pathogens and particulates.
- Olfaction – The upper nasal cavity contains olfactory receptors responsible for smell.
Under normal conditions, the nasal and paranasal sinus mucosa produce approximately 1 liter of mucus per day, primarily via goblet cells and submucosal glands. This mucus is transported posteriorly by coordinated ciliary motion in a process known as mucociliary clearance, ultimately being swallowed unconsciously.
Clinical Manifestations of Postnasal Drip
Postnasal drip occurs when mucus becomes excessively thick, voluminous, or poorly drained, accumulating in the nasopharynx and trickling down into the oropharynx. This may result in:
- Throat clearing and globus sensation
- Persistent, non-productive cough
- Morning or nocturnal cough exacerbation
- Hoarseness or dysphonia
- Halitosis and nausea
- Excessive swallowing or need to expectorate mucus
Notably, elderly patients or those with chronic rhinitis may present with throat symptoms alone, without overt nasal obstruction or rhinorrhea.
Etiological Factors
Postnasal drip is not a singular disease but a clinical syndrome secondary to various underlying conditions. It generally involves mucus overproduction, altered viscosity, or impaired clearance.
🔹 Primary Causes
- Allergic Rhinitis – Exposure to allergens (e.g., pollen, dust mites, animal dander) elicits IgE-mediated inflammation and increases serous nasal secretions.
- Viral Upper Respiratory Infections – Induce mucosal edema and hypersecretion, sometimes blocking sinus.
- Environmental Factors – Dry, cold air may trigger reactive mucus production.
- Anatomical Variations – Septal deviation or nasal polyps impair normal drainage pathways.
🔸 Secondary or Contributing Conditions
- Gastroesophageal reflux disease (GERD)
- Pregnancy-related rhinitis
- Exposure to irritants (smoke, pollution, chemicals)
- Certain medications (ACE inhibitors, hormonal therapies)
- Chronic pulmonary conditions (COPD, asthma)
- Enlarged adenoids or chronic adenoiditis in children
- Spicy food and hot beverages – transiently increase secretion via autonomic stimulation
Management Principles
Management of postnasal drip is aimed at reducing secretion, improving mucociliary clearance, and minimizing inflammatory stimuli. Empiric therapy may include:
- Antihistamines (especially second-generation agents for fewer sedative effects)
- Mucolytics or expectorants
- Intranasal corticosteroids
- Antihistamine or corticosteroid nasal sprays
- Saline nasal irrigation
- Supportive care – increased hydration, environmental control, head-of-bed elevation during sleep
When to Seek Specialist Evaluation
Referral to an otolaryngologist is advised when the following are observed:
- Purulent, foul-smelling, or blood-streaked nasal discharge
- Associated fever, facial pressure, or orbital discomfort
- Persistent hoarseness, globus sensation, or dysphagia
- Unilateral nasal obstruction or anosmia
- Refractory symptoms despite appropriate medical therapy
Such features may indicate conditions requiring endoscopic examination or imaging, such as sinonasal neoplasms, nasal polyposis, deviated septum, or other significant ENT pathologies.
