Why does your nose run in cold air?

You step outside on a cold winter day, and within a few minutes your nose begins to drip. The effect often becomes more noticeable during running, skiing, or brisk walking, but it can also happen while standing still. The discharge is usually clear and watery, and the symptoms often improve shortly after you return to a warm environment.

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A runny nose in cold weather is usually not caused by a cold, allergy, or infection. It is mainly a physiological response that occurs because the nose must warm, humidify, and filter the air before it reaches the lungs. When the air is cold and dry, the nasal lining has to work harder. Fluid production may then exceed the amount the nose can retain.

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The nose conditions the air before it reaches the lungs

The nasal cavity is more than a passage for air. It is part of the body’s protective system and helps adapt inhaled air to the conditions required by the lower airways.

The nose helps to:

• warm cold air

• add moisture

• filter dust and particles

• trap microorganisms

• regulate airflow

• support the sense of smell

• protect the throat, trachea, and lungs

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The nasal lining has a large surface area and is rich in blood vessels. As air passes through the nose, heat is transferred from the blood to the air. At the same time, water evaporates from the mucosal surface and increases the humidity of the inhaled air.

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This happens very quickly. Before the air reaches the trachea, it has usually become considerably warmer and more humid than the outdoor air. The colder and drier the air is, the more heat and moisture the nose must provide.

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Cold air contains little water

Cold air can hold less water vapour than warm air. This means that the relative humidity may be high while the actual amount of water in the air remains low.

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When dry winter air enters the nose, the lining must release more water to humidify it. Fluid therefore evaporates from the mucosa with every breath.

This increases the need for:

• fluid delivery to the nasal lining

• blood flow in the nasal vessels

• activity in mucus-producing glands

• regulation through the autonomic nervous system

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If fluid production exceeds evaporation and drainage towards the throat, secretions collect in the nasal passages. The excess then runs out through the nostrils.

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This explains why the problem is often most noticeable on cold and dry days. The trigger is not necessarily temperature alone, but the combination of low temperature and low absolute humidity.

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The nasal lining reacts quickly to temperature changes

The nasal mucosa contains nerve endings that respond to temperature and chemical stimuli. When cold air reaches the lining, the drop in temperature is detected almost immediately.

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These signals influence the autonomic nervous system, which regulates blood vessels and glands in the nose. The response may include:

• increased blood flow

• dilation of blood vessels

• increased gland activity

• more watery secretion

• swelling of the mucosa

• altered airflow resistance

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This is a reflex response. The rest of the body does not need to feel cold for the nose to react. Exposure of the nasal lining to cold air is enough.

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The response can therefore begin very quickly, often within the first few minutes outdoors.

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The discharge is usually thin and clear

The fluid that runs from the nose in cold weather is usually watery. It consists mainly of water, but also contains mucus substances, electrolytes, antibodies, and other protective proteins.

The thin secretion helps to:

• keep the mucosa moist

• trap particles

• protect surface cells

• support the transport of mucus towards the throat

• maintain normal ciliary function

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Cilia are tiny moving structures on the surface of the mucosal cells. They transport mucus, particles, and microorganisms towards the throat, where the material is swallowed or removed.

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During a viral cold, the discharge may become thicker because of inflammation, immune cells, and changes in mucus composition. In a simple cold-air response, it usually remains clear and watery.

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Some of the fluid may come from condensed exhaled air

Not all of the fluid is necessarily produced by the glands. Some may come from water vapour in exhaled air.

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Air leaving the lungs is warm and humid. When it meets the colder areas inside the nose, some of the water vapour may condense into liquid. The same principle can be seen when warm breath becomes visible in cold air.

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The nose normally attempts to recover both heat and moisture during exhalation. In cold conditions, this process may leave more fluid inside the nasal passages.

A runny nose may therefore result from a combination of:

• increased glandular secretion

• fluid moving towards the mucosal surface

• condensation from exhaled air

• reduced evaporation in some areas

• temporarily altered mucus transport

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It is difficult to determine how much each mechanism contributes in one person, but together they can explain the noticeable watery discharge.

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Blood vessels help warm the air

The nasal lining contains a dense network of blood vessels that functions as a heat exchanger.

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When cold air enters, blood flow in the mucosa may increase. Warm blood transfers heat to the inhaled air before it reaches the more sensitive lower airways.

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The increased blood flow can also make the lining swell. Some people therefore experience both a runny and blocked nose in the cold.

This may cause a combination of:

• increased secretion

• narrower nasal passages

• greater airflow resistance

• frequent sniffing

• a shift towards more mouth breathing

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The degree of swelling varies between individuals. Some mainly experience watery discharge, while others notice congestion as the dominant symptom.

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Physical activity increases the demand on the nose

During exercise, ventilation increases. You inhale far more air per minute than you do at rest.

The nose must then:

• warm a larger volume of air

• add more moisture

• filter more particles

• manage faster airflow

• compensate for greater evaporation

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The result may be greater fluid production and a more pronounced runny nose.

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At higher intensities, many people also begin breathing more through the mouth. This allows part of the air to bypass the nose’s warming and humidifying system. It may reduce the immediate demand on the nose, but it increases exposure of the throat and lower airways to cold, dry air.

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Winter athletes may be particularly affected because they combine:

• high ventilation

• prolonged cold exposure

• dry air

• wind

• repeated training sessions

• high total airway load

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Cross-country skiers and other endurance athletes therefore often report a runny nose, nasal congestion, cough, or airway irritation.

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Wind strengthens the effect of cold exposure

Wind removes the warm and humid layer of air that can form in front of the nose and mouth. The nasal lining is then exposed more directly to cold, dry airflow.

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Headwind also increases airflow through the nose, especially during cycling, running, and skiing.

Wind may therefore contribute to:

• faster cooling of the mucosa

• greater evaporation

• more irritation

• increased secretion

• stronger cold sensation in the face

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A scarf, buff, or mask covering the nose and mouth can reduce this effect by retaining some of the warmth and moisture from exhaled air.

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Some people react more strongly than others

There are large individual differences in how much the nose runs in cold weather. Some people have almost no symptoms, while others need to wipe their nose continuously.

The reaction may be influenced by:

• sensitivity of the nasal lining

• autonomic nervous-system activity

• nasal anatomy

• allergies

• asthma

• previous airway problems

• age

• medication use

• adaptation to cold

• exercise intensity

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People with already sensitive mucosa may react more strongly. This includes some individuals with non-allergic rhinitis, allergic rhinitis, or chronic nasal irritation.

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Even people without a diagnosed nasal condition may vary greatly in the strength of the reflex response.

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Cold-induced rhinitis is often non-allergic

Rhinitis refers to inflammation or irritation of the nasal lining and may cause a runny nose, congestion, sneezing, and itching.

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In allergic rhinitis, symptoms are triggered by allergens such as pollen, house dust mites, or animals. A runny nose triggered by cold air is usually not an allergic reaction.

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In some people, the cold response is part of non-allergic rhinitis. In this condition, the nose reacts strongly to physical or chemical stimuli without the immune system responding to a specific allergen.

Common triggers may include:

• cold air

• temperature changes

• smoke

• perfume

• strong smells

• alcohol

• spicy food

• air pollution

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The symptoms can resemble allergy, but itching in the eyes and nose is often less prominent. Allergy tests are usually negative.

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Some people have a combination of allergic and non-allergic rhinitis. Cold air may then intensify symptoms that are already present.

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How to distinguish a cold-air response from a viral cold

A runny nose in cold air and a viral cold may look similar, but the timing is often different.

Feature	Cold-air runny nose	Viral cold
Onset	Shortly after exposure to cold	Gradually over hours or days
Discharge	Usually clear and watery	Often clear at first, then thicker
Duration	Often improves indoors	Continues throughout the day
Fever	Usually absent	May occur
Sore throat	Usually absent	Common
General illness	Usually absent	May be present
Cough	Not typical on its own	Common
Trigger	Cold or dry air	Viral infection

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Cold air itself does not create a viral infection. Colds are caused by viruses.

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Winter may still increase the risk of infection indirectly because people spend more time indoors, have closer contact, and are exposed to dry indoor air. Cold exposure may also affect local defence mechanisms in the airways, but this is different from becoming infected simply because you were cold.

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Skier’s nose can become a persistent problem

The term skier’s nose is sometimes used to describe pronounced nasal discharge in people who train frequently in cold air.

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In winter athletes, repeated exposure may contribute to greater sensitivity of the mucosa. High ventilation and cold, dry air can affect both the nose and the lower airways over time.

Possible symptoms include:

• persistent nasal discharge

• nasal congestion

• cough

• mucus in the airways

• throat irritation

• wheezing

• shortness of breath during exercise

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A runny nose alone is usually harmless. If it is accompanied by cough, wheezing, or reduced performance, exercise-induced bronchoconstriction or another airway condition may need to be considered.

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This is particularly relevant for people with asthma or previous respiratory symptoms.

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Mouth breathing does not necessarily solve the problem

When the nose becomes blocked or starts to run, many people begin breathing through the mouth. This may feel easier in the short term, especially during hard exercise.

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Mouth breathing bypasses much of the nose’s warming and humidifying function. Cold air then reaches the throat and lower airways more directly.

This can contribute to:

• dry mouth

• sore throat

• cough

• airway irritation

• chest discomfort

• increased risk of airway narrowing in susceptible people

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During low-intensity activity, nasal breathing may be useful as long as it feels natural. At high intensity, mouth breathing is often necessary to meet the body’s ventilatory demands.

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The goal is therefore not to force nasal breathing in every situation, but to reduce unnecessary exposure when practical.

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A scarf or buff may reduce the symptoms

Covering the nose and mouth is a simple measure that may reduce the symptoms in some people.

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The material traps heat and moisture from exhaled air. The next breath is therefore less cold and dry.

This may reduce:

• cooling of the nasal lining

• water evaporation

• irritation

• the need for secretion

• discomfort in the throat and airways

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The fabric should not be so tight that breathing becomes difficult or so wet that it becomes uncomfortable. During exercise, it may need to be adjusted according to intensity and temperature.

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Special masks and heat-exchange devices may be useful for some winter athletes or people with pronounced cold-induced airway symptoms.

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Saline can support the nasal lining

Saline spray or nasal rinsing may help keep the mucosa moist and remove particles and excess mucus.

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Isotonic saline has approximately the same salt concentration as body fluids and is generally well tolerated. Hypertonic saline has a higher salt concentration and may reduce swelling in some people, but can also sting or irritate more.

Saline may be useful:

• before cold exposure

• after exercise

• in dry indoor air

• when secretions feel thick

• with simultaneous irritation from dust or particles

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It is important to use clean equipment and appropriate water for extensive nasal rinsing. Untreated tap water should not be used indiscriminately in nasal irrigation systems.

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Saline does not necessarily stop the reflex response itself, but it may improve comfort and support normal mucosal function.

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Medication is rarely needed for mild symptoms

For most people, a runny nose in cold air is a harmless problem that does not require medical treatment.

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For severe symptoms, a doctor may sometimes consider a nasal spray that reduces secretion. Anticholinergic nasal spray containing ipratropium may help with watery rhinorrhoea, particularly in non-allergic rhinitis.

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This type of spray reduces glandular secretion but usually has less effect on congestion.

Possible considerations include:

• nasal dryness

• irritation

• nosebleeds

• correct dosing

• other medical conditions

• possible contraindications

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Decongestant nasal sprays may reduce blockage for a short time, but they are not specifically intended for watery discharge. Prolonged use can cause rebound congestion and should be avoided.

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Allergy medication has limited effect when the reaction is not allergic. Treatment should therefore be matched to the cause rather than only the symptom.

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Practical measures on cold days

The symptoms cannot always be prevented completely, but several strategies may make them easier to manage.

You can try to:

• cover the nose and mouth with a scarf or buff

• warm up gradually before high-intensity exercise

• use nasal breathing during low-intensity activity

• wipe the nose gently rather than rubbing the skin

• use saline for dry or irritated nasal lining

• reduce exposure to smoke and strong smells

• replace a wet buff or mask during long sessions

• schedule the hardest sessions for milder conditions

• breathe more calmly when the activity allows it

• protect the skin around the nose with a mild barrier cream

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Frequent wiping can irritate the skin beneath the nose. Soft tissue and an unscented moisturiser or barrier cream may reduce soreness.

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There is no need to avoid physical activity simply because the nose runs. The aim of the measures is mainly to improve comfort.

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When the symptoms should be assessed

Clear fluid from both nostrils that appears in cold weather and improves in warmth is usually a normal response.

It may be sensible to seek medical assessment if the symptoms:

• continue regardless of temperature

• significantly reduce quality of life

• are accompanied by marked nasal congestion

• occur with wheezing or shortness of breath

• cause repeated nosebleeds

• are accompanied by facial pain or fever

• lead to persistent loss of smell

• mainly affect one nostril

• involve bloody or foul-smelling discharge

• begin after a head injury or operation

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Persistent clear watery fluid from only one nostril, particularly after head trauma or nasal surgery, may require assessment for a cerebrospinal fluid leak. This is rare, but medically important.

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Acute breathing difficulty, major swelling of the face or throat, or rapidly developing allergic symptoms require urgent medical care.

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Summary

The nose runs in cold air because it must warm and humidify inhaled air before it reaches the lungs. Cold air contains little water, so the nasal lining must add more moisture. Increased blood flow, nerve activity, glandular secretion, and condensation from exhaled air can together produce an excess of clear and watery fluid. The reaction often becomes stronger during exercise because ventilation increases. For most people, this is a normal and harmless response. Covering the nose and mouth, warming up gradually, and using saline may reduce the symptoms. Persistent, one-sided, bloody, or respiratory symptoms should be assessed for other possible causes.

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Sources

• Cole, P. (2000). The respiratory role of the upper airways. Respiratory Care Clinics of North America, 6(1), 1–18.

• Silvers, W. S. (1991). The skier’s nose: A model of cold-induced rhinorrhea. Annals of Allergy, 67(1), 32–36.

• Settipane, R. A. & Kaliner, M. A. (2013). Nonallergic rhinitis. American Journal of Rhinology & Allergy, 27(Suppl. 1), S48–S51.

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