Why does the nose produce excess mucus in response to cold temperatures?

Why Your Nose Runs in Cold Weather

The nose produces excess mucus in cold temperatures because the nasal mucosa must invest significantly more water to warm and humidify cold, dry air to body temperature and full saturation before it reaches the lungs, resulting in visible nasal secretions (rhinorrhea). 1

The Physiological Mechanism

Primary Air Conditioning Function

• The nose functions to condition inhaled air from ambient temperatures ranging from -42°C to 48°C and relative humidities from 0% to 100%, bringing it to nearly alveolar conditions (body temperature and fully saturated with water vapor) by the time it reaches the nasopharynx 1

• When exposed to cold, dry air (CDA), the nasal mucosa must transfer substantial amounts of water to the inspired airstream—studies show the water gradient increases from approximately 297.6 mg at 5 L/min flow to 794.1 mg at 20 L/min flow rates 1

The Cold Air Response

• Exposure to cold, dry air triggers a significant increase in nasal secretions (30 ± 10 mg increase from baseline) compared to warm, moist air (0 ± 1 mg change), with this difference being highly significant (p < 0.009) 1

• This response involves release of inflammatory mediators: histamine levels increase from 3.9 ± 1.2 to 10.6 ± 2.7 ng/ml, and TAME esterase activity also rises significantly (p < 0.01) after cold air exposure 1

• The nasal mucosa invests water into the airstream through both evaporation from the mucosal surface and active glandular secretions, with the parasympathetically-driven nasal glands being major contributors to secretion volume 1

Key Factors Influencing the Response

Mucosal Temperature

• Nasal mucosal temperature is critical to conditioning capacity—warming the nasal mucosa from 32.2°C to 33.1°C significantly increases the nose's ability to humidify air (from 1324 ± 152 mg to 1669 ± 312 mg water, p < 0.05) 1, 2

• Cold air exposure lowers nasopharyngeal temperatures substantially (from 34.6°C to as low as 28.2°C at higher flow rates in normal subjects) 1

Airflow Dynamics

• Turbulent airflow patterns in the nasal cavity enhance contact between air and the mucosal layer, optimizing humidification, warming, and cleaning functions even at low air velocities 3

• The relative humidity of air in the nasopharynx remains at 100% regardless of inspired air conditions, demonstrating the nose's remarkable conditioning capacity 1, 4

Clinical Considerations

Individual Variability

• There is wide individual variability in nasal conditioning capacity (coefficient of variation averaging 14.7%), though the response is reproducible within individuals across multiple testing sessions 1

• Individuals with atopy (allergic predisposition) show impaired baseline conditioning capacity compared to non-allergic subjects (water gradient 1,430 ± 45 mg vs 1,718 ± 141 mg, p = 0.02) 4

The "Runny Nose" Phenomenon

• The visible nasal discharge ("runny nose") in cold weather represents the overflow of secretions beyond what can be absorbed or evaporated—the nose produces more fluid than can be immediately utilized for air conditioning 1

• This is a normal physiological response, not a pathological condition, though individuals with pre-existing nasal hyperreactivity may experience more pronounced symptoms 5

Recovery During Exhalation

• Approximately 30% of heat and moisture is recovered during exhalation through the nose, though this recovery does not prevent the secretory response to cold air 1