Your body's instincts in the cold aren't always aligned with your needs.
Each winter, the body makes a quiet bargain: when cold air tightens the chest and congestion narrows the nasal passages, the mouth opens to meet the lungs' demand for more. It is an ancient reflex, efficient in the moment, but one that trades the nose's remarkable conditioning work—warming, humidifying, filtering—for raw exposure to frigid, unguarded air. The comfort we feel is real; the cost, invisible until it arrives as irritation, coughing, or worse. Understanding this small physiological negotiation is the first step toward breathing more wisely through the cold months.
- Cold temperatures and physical exertion create an urgent demand for air that the mouth satisfies faster than the nose can, making the habit feel not just natural but necessary.
- By bypassing the nose, the body loses its built-in air-conditioning system—the warming, moistening, and filtering functions that protect the throat, trachea, and bronchi from frigid, unfiltered air.
- The consequences accumulate: dry throat, bronchial irritation, persistent coughing, and heightened risk for those already living with asthma or chronic respiratory conditions.
- Simple interventions—a scarf over the nose and mouth, steady hydration, and avoiding abrupt transitions from warm to cold environments—can restore much of the protection that nasal breathing provides.
- The deeper tension is between instinct and physiology: what the body reaches for in a cold moment is not always what the body actually needs.
When the cold arrives and the pace quickens—a brisk walk, a winter jog—the mouth opens almost without thought. Carolina Carvajal, who coordinates the otolaryngology program at Universidad Andrés Bello's medical technology school, explains the calculation the body is making: exertion increases the lungs' demand for air, and the mouth's wider opening delivers that volume with less resistance than the nose can offer. Cold temperatures compound the problem by constricting the blood vessels in the nasal passages, producing congestion that makes nasal breathing feel genuinely difficult. The mouth becomes the path of least resistance, both physically and psychologically.
What this reflex sacrifices, however, is considerable. The nose was designed precisely for conditions like these—it warms incoming air, adds moisture, and uses its lining and hair-like cilia to trap particles, microorganisms, and allergens before they reach the lungs. In dry, frigid air, that conditioning function is not a luxury but a shield. Strip it away, and cold air enters raw and unfiltered, irritating the throat, trachea, and bronchi, triggering coughing, and posing serious risk to anyone with asthma or chronic lung disease.
The remedies are accessible: a scarf or neck gaiter covering both nose and mouth recreates some of the nose's warming work; hydration keeps tissues resilient; and avoiding sudden plunges from heated interiors into bitter cold gives the respiratory system time to adapt. The broader lesson Carvajal's guidance points toward is one of gentle self-awareness—the instinct that feels easiest in a cold moment may quietly work against the body over time, and a small, conscious adjustment in how we breathe can make a meaningful difference.
When the temperature drops and you're moving fast—walking briskly to catch a bus, jogging through winter air—your mouth opens. It feels natural. It feels necessary. The cold seems to demand it. But this reflex, common as it is, carries a cost that most people never consider.
Carolina Carvajal, who coordinates the otolaryngology program at Universidad Andrés Bello's medical technology school, explains what's happening in those moments. The body is making a calculation: when you're exerting yourself in cold conditions, your lungs want more air, and they want it fast. The mouth, with its wider opening, delivers that volume more efficiently than the nose can. There's less resistance. The air flows. It feels easier, especially when you're breathing deeply.
Cold itself plays a role too. Low temperatures trigger changes in the blood vessels lining the nasal passages, creating that familiar sensation of congestion—a stuffy nose that makes nasal breathing feel impossible. So the mouth becomes the path of least resistance, literally and psychologically. The mouth's larger cavity reinforces the perception that breathing this way is simply more comfortable, more effective.
But comfort and physiology are not the same thing. The nose, Carvajal emphasizes, was built for this job. It warms the air before it reaches your lungs. It adds moisture. It traps particles, microorganisms, and allergens using the nasal lining and tiny hair-like structures called cilia. In cold, dry conditions especially, this conditioning function becomes critical—it protects the delicate tissues of your throat, trachea, and bronchi from the irritating shock of raw, frigid air.
When you bypass the nose and breathe through your mouth, that protection disappears. Cold air enters unfiltered and unconditioned. The result is predictable: a dry throat, irritation in the trachea and bronchi, coughing triggered by the cold itself, and a general respiratory discomfort that can be severe for people with asthma or other chronic lung conditions. The habit that feels easier in the moment creates problems that linger.
The fix is straightforward, though it requires intention. A scarf or neck gaiter that covers both nose and mouth warms the air you inhale, mimicking some of what your nose would do naturally. Staying hydrated helps too. Avoiding sudden temperature swings—stepping from heated indoors into brutal cold—gives your respiratory system time to adjust. And if symptoms persist, a doctor's visit becomes necessary.
The larger lesson is this: your body's instincts in the cold are not always aligned with your body's actual needs. What feels right in the moment can work against you over time. Breathing through your mouth on a winter day is a small choice, but it's one worth reconsidering.
Citas Notables
Our nose is physiologically designed to be the primary breathing pathway, especially in cold environments.— Carolina Carvajal, otolaryngology coordinator, Universidad Andrés Bello
Cold air entering through the mouth reaches the airways less conditioned, causing throat dryness, tracheal irritation, and greater respiratory discomfort, particularly for people with asthma.— Carolina Carvajal
La Conversación del Hearth Otra perspectiva de la historia
Why does the nose feel blocked in the cold if it's actually still working?
The blood vessels in your nasal lining constrict in response to cold, which creates swelling and that sensation of congestion. It's a real physical response, but it doesn't mean the nose has stopped functioning—it's just harder to breathe through, so people switch to their mouth.
So the nose is still filtering and warming air even when it feels blocked?
Exactly. Even with congestion, the nose is still doing its job. But the sensation of difficulty makes people abandon it, which is the real problem.
Is there a difference between mouth breathing during exercise and mouth breathing while just walking around?
The intensity matters. During hard exercise, your body genuinely needs more air volume, so mouth breathing is more understandable. But even then, the cost to your airways is the same—unfiltered, cold air reaching tissues that aren't prepared for it.
What about people who live in consistently cold climates? Do they adapt?
That's a good question the article doesn't address. But the damage—throat irritation, bronchial irritation—would likely accumulate over time rather than improve. Adaptation doesn't change the physiology.
If someone already has asthma, is mouth breathing in cold weather actually dangerous?
Yes. For someone with asthma, cold air is already a trigger. Unfiltered, unconditioned cold air hitting the airways directly can provoke an attack or serious inflammation. It's not just uncomfortable—it's a real health risk.