Post Nasal Drip
Post-nasal drip — the sensation of mucus flowing from the nose and sinuses down the back of the throat — is one of the most common and most frequently persistent complaints in ENT practice. It causes throat irritation, a chronic cough, a constant need to clear the throat (throat-clearing), and in many patients significantly disturbs sleep. Post-nasal drip is not itself a diagnosis but a symptom — a reflection of either excessive mucus production, abnormally thick mucus, impaired clearance, or heightened sensory awareness. Identifying the underlying cause is essential before treatment can be rationally selected.
Normal Mucus Physiology
The nasal and sinus lining produces approximately one to two litres of mucus per day under normal conditions — a fact that surprises most patients, who assume normal mucus production is far lower. This mucus is propelled by millions of microscopic cilia on the epithelial surface at approximately 700–1,000 beats per minute, moving the mucus blanket toward the nasopharynx at a rate of approximately 6mm per minute. Under normal circumstances, this continuous flow of mucus is swallowed without conscious awareness.
Post-nasal drip becomes symptomatic when:
- Mucus production is increased (infection, allergy, rhinitis)
- Mucus becomes thicker and stickier (dehydration, chronic infection, allergy)
- Mucociliary clearance is impaired (viral infection, chronic sinusitis, ciliary dysfunction)
- Laryngopharyngeal reflux (LPR) causes the posterior pharyngeal mucosa to produce excess mucus as a protective response to acid, even in the absence of increased nasal mucus
- Sensory thresholds are altered — some patients have heightened awareness of normal mucus flow, particularly following a viral illness that sensitises the posterior pharyngeal mucosa
Causes in Detail
Allergic Rhinitis
The single most common cause of post-nasal drip. Allergen exposure triggers an IgE-mediated immune response in the nasal mucosa, producing oedema, sneezing, and watery secretions from activated goblet cells and submucosal glands. In house dust mite sensitivity — the dominant perennial allergen in Sydney’s humid coastal climate — post-nasal drip is typically a year-round complaint, often worse overnight and in the early morning when dust mite allergen levels are highest in bedding. In pollen-sensitive patients it is seasonal. Treatment of the underlying allergy substantially reduces post-nasal drip.
Non-Allergic Rhinitis
A heterogeneous group of conditions characterised by nasal symptoms — including post-nasal drip — without an IgE-mediated mechanism. Subtypes include:
- Vasomotor rhinitis (idiopathic non-allergic rhinitis): Triggered by changes in temperature or humidity, strong smells, perfumes, smoke, air conditioning, alcohol, or spicy food. The nasal mucosa has an exaggerated response to these non-specific triggers through abnormal autonomic innervation. Watery discharge and post-nasal drip are the dominant symptoms. Does not respond to antihistamines (because it is not histamine-mediated); responds to topical ipratropium bromide (Atrovent nasal spray) and intranasal corticosteroids.
- Gustatory rhinitis: Watery rhinorrhoea and post-nasal drip triggered specifically by eating — particularly hot or spicy foods. Mediated by cholinergic reflexes. Topical ipratropium before meals can provide relief.
- Rhinitis of pregnancy: Hormonal changes (elevated oestrogen and progesterone) cause mucosal engorgement and increased secretions in the third trimester. Resolves after delivery.
- Drug-induced rhinitis: A number of medications cause nasal symptoms including post-nasal drip, including ACE inhibitors (a well-recognised cause of chronic cough and post-nasal drip), beta-blockers, aspirin and NSAIDs, and prolonged use of topical decongestant sprays (rhinitis medicamentosa from oxymetazoline rebound).
Chronic Rhinosinusitis
Chronic inflammation of the sinus lining drives ongoing mucus production — often thick, discoloured, and difficult to clear — with drainage into the nasopharynx. Post-nasal drip in CRS is typically associated with nasal obstruction, facial pressure, and anosmia. Treatment of the underlying CRS — medically and surgically — substantially reduces the symptom burden.
Laryngopharyngeal Reflux (LPR)
LPR — the backflow of gastric contents (acid and non-acid) into the larynx and pharynx — produces a spectrum of symptoms that significantly overlap with post-nasal drip: the sensation of mucus in the throat, frequent throat-clearing, chronic cough, hoarseness, and a feeling of something in the throat (globus). LPR may co-exist with genuine post-nasal drip, and distinguishing them is clinically important. LPR is suggested by the absence of anterior nasal symptoms (congestion, sneezing, rhinorrhoea) with predominant throat symptoms, and by the presence of posterior laryngeal erythema or mucosal swelling on nasendoscopy. Treatment with dietary modification, anti-reflux positioning, and proton pump inhibitors can substantially reduce LPR-related symptoms.
Anatomical Factors
A significantly deviated nasal septum creates turbulent airflow and localised mucosal drying and irritation, producing abnormal secretions. Large inferior turbinates generate excess mucus. Septal perforations disrupt normal mucus flow patterns. Addressing these structural issues can reduce the mucus burden reaching the nasopharynx.
Age-Related Changes
As people age, the mucous glands of the nasal and sinus lining undergo changes in secretory regulation, producing thicker, more viscous mucus that is harder to clear and more likely to produce symptomatic post-nasal drip. Dehydration — increasingly common in older adults — dramatically worsens mucus viscosity.
Distinguishing True Post-Nasal Drip from Throat Hypersensitivity
An important subgroup of patients — particularly those who have experienced viral illness (including COVID-19) — develop persistent throat symptoms with the sensation of mucus, throat-clearing, or a lump in the throat, in the absence of identifiable sinonasal disease on endoscopy or CT scanning. This condition has various names: post-viral sensory sensitisation, throat hypersensitivity, functional throat symptoms, or — in the neurological framing — central sensitisation of the laryngopharyngeal sensory system.
In these patients, the sensation of post-nasal drip is real and distressing but reflects altered sensory processing rather than excessive mucus. Treatment is not directed at reducing mucus (which is not the problem) but at managing sensory sensitisation through speech pathology techniques, low-dose gabapentin or amitriptyline, and cognitive approaches to managing the symptom.
Assessment
- History: The character, timing, and triggers of symptoms are key. Watery, clear, and worse with seasonal or allergen exposure suggests allergy. Thick, coloured, associated with nasal obstruction suggests CRS. Predominantly throat-based without nasal symptoms, worse after meals and supine, suggests LPR. Constant and unchanged despite all treatment suggests sensory component.
- Nasal endoscopy: Essential. Identifies polyps, purulent discharge from sinus ostia, turbinate hypertrophy, anatomical obstruction, and the appearance of the nasopharynx and posterior pharyngeal wall. The presence of cobblestoning on the posterior pharyngeal wall suggests chronic post-nasal drip or LPR.
- CT sinuses: Where CRS is suspected clinically. A normal CT makes sinus disease an unlikely primary cause.
- Allergy testing: Skin prick testing or specific IgE where allergic rhinitis is suspected.
- Laryngoscopy: Flexible nasendoscopy to the larynx assesses the vocal cords and posterior commissure for changes consistent with LPR.
Treatment
Treatment is completely determined by the underlying cause:
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Dr Roth’s Clinical Perspective
Post-nasal drip as a presenting complaint is one of the most symptom-description-sensitive complaints in ENT — patients describe the same sensation for completely different underlying causes, and the investigation needs to start with understanding what specifically they are experiencing. True post-nasal drip from excess mucus production is managed differently from the throat sensation caused by laryngopharyngeal reflux, which is different again from a habitual throat clearing pattern that has created mucosal irritation. Treating for sinusitis because a patient reports post-nasal drip, without excluding these other causes, is a common error that results in treatment that does not help.
— Dr Jason Roth, MBBS, FRACS (ORL-HNS), IBCFPRS
Specialist Otolaryngologist & Head and Neck Surgeon
Specialist registration — Otorhinolaryngology, Head & Neck Surgery
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