Nose vs. Mouth breathing

My nose allows ‘life energy’ into my body and defends my lungs from invaders. Furthermore, it’s mainly through my mouth that disease sneaks into my body. Therefore, breathing through my nose is quality, while breathing through my mouth is quantity.

Two alternative air channels

Ever since the time we lived in caves, the air around us has been contaminated. Humans’ exposure to hazardous substances in the form of dust, smoke particles from fires, volcanic ashes, pollen, mold, microbes, etc., has been going on for ages. Nowadays, there are many artificial pollutants on top of natural ones. These substances are unwanted ‘guests’ in the lungs. 

Humans have developed cleaning and filtering features in the body following evolutionary processes. For example, particles entering my breathing system end up in my digestive system and are eliminated there. I have also evolved to have a natural sterilizing mechanism, which fights unwanted invaders such as bacteria, viruses, and fungi.

Because air is vital to my existence, having two alternative air channels improves my survival chances, it’s a sort of insurance. I can use my nose and mouth channels in different combinations, but I don’t tend to use them simultaneously when I breathe (some people do).

Let’s go sightseeing and follow the air as it journeys from the nostrils to the lungs. First, we’ll look at nose breathing and then compare it to mouth breathing.

Nose inhaling

The air I inhale through my nose goes through a filtering process. I have evolved to have several filtering mechanisms because once pollutants reach my lungs, it takes intensive body efforts to remove them. Therefore, the more particles are filtered before they reach my lungs, the fewer resources my body needs for a cleanup.


Initial entrance filtration

The fine nasal hair covering my nostrils traps rough pollutants such as dust and pollen. The bigger airborne particles collect on the fine hair. The mucus coating the sides of my nose functions as a wet sticky filter and traps smaller particles and pollutants that pass my hair filter.

The nasal cavity

Continuing to follow the inhaled air, we get to the nasal cavity. This inner headspace is about the size of a tennis ball, and its inside resembles a maze with narrow passages.

Nasal cavity maze – about the size of a tennis ball

Nasal cavity odor detection

The air passing through my nasal cavity goes through a sampling and monitoring process. Sharp smell sensors send information to my brain for evaluation. Smell indications allow me to reject or accept the air I inhale. For example, if the air smells pleasant or neutral, I will enable it to continue further into my body. Still, if it smells foul or unpleasant, I reject the air by holding my breath and immediately exhaling. There are smells I find to be calming, and there are those that stimulate.

In the past, humans relied heavily on their sense of smell for survival. Every inhale provided information crucial to finding food, assessing if the food was rotten or edible, spotting danger, and finding a mating partner. Later in our evolution, we shifted towards relying on our visual sense as the primary sensual source of information for survival.

Nasal cavity disinfection

I have two important disinfecting mechanisms in my nasal cavity. These are my first line of defense against unwanted microbes seeking to settle in my body’s humid and warm conditions. Microbes may cause airway inflammation or a lung infection.

1. Mucus disinfection

The mucus which covers my nasal cavity maze is a sterilizer. It has unique qualities that trap bacteria and viruses and kills them. Unfortunately, mucus sterilizing is temperature dependant. It’s less effective when the nose temperature is lower than the body temperature of 37⁰ C  (98.6⁰ F). The colder the air I inhale, the lower the sterilizing effectivity. That is one of the reasons I get influenza mostly during the winter. Keeping my nose and nasal cavity warm may reduce the chances of viruses or bacteria sneaking into my body through my nose.

2. Nitric oxide disinfection

The air passing through my nasal cavity blends with a gas called Nitric-Oxide. It’s a toxic gas, but in minimal quantity, it’s beneficial and plays a central role in a few breathing processes. This gas is released from my sinuses into my nasal cavity and mixes with the passing air.

In the nasal cavity, Nitric-Oxide functions as an effective sterilizer preventing unwanted airborne invaders such as bacteria, viruses, or fungus from infiltrating my body. Nitric-Oxide not only disinfects on its own but also promotes mucus generation, boosting further sterilization.

Other fantastic Nitric oxide functions

Nitric Oxide dilation

Another vital function of Nitric-Oxide is dilating my airways and blood vessels. It opens my airways wider, which improves airflow. Likewise, it dilates blood vessels in my lungs and increases blood exposure to Oxygen, allowing better gas exchange.

Nitric Oxide improves air distribution

Nitric-Oxide also distributes the air inside my lungs more evenly, curbing the negative influence of gravity on air distribution. Therefore, air treated with Nitric-Oxide leads to better Oxygen absorption.

Nitric Oxide promotes lung elasticity

As I age, my lungs gradually become less elastic. That reduces my lung functionality. Nitric-Oxide helps in delaying the lungs from getting rigid.

 Other important nitric oxide functions

For over 100 years, Nitroglycerine ingestion in small amounts was used to relieve heart patients; it’s still in use today. Nitric-Oxide released from Nitroglycerine contributes to blood vessel dilation, allowing better blood supply to the heart and Oxygen supply to the cells.

Nitric-Oxide relaxes the penis muscles and allows the penis chambers to easier fill with the blood needed for an erection. Nitric-Oxide is the active ingredient in the revolutionary Viagra pill. Not only men but women may also benefit from Nitric-Oxide’s magical effects. It improves vaginal blood flow and relaxes vaginal muscles.

Our nose is not the only source of Nitric-Oxide in the body, but the nose is a significant source.

Nasal cavity humidification

The air passing through my nasal cavity maze collects moisture on its way and gets humidified. Humid air allows much better Oxygen absorption in my lungs compared to dry air.

Nasal cavity temperature regulation

The temperature of the air passing through the narrow maze of my nasal cavity is regulated. The maze allows efficient heat exchange. When air leaves my nasal cavity toward my lungs, it’s close to my body temperature of 37⁰ C (98.6⁰ F). Oxygen is much better absorbed when the air reaching my lungs is close to my body temperature.

Airflow regulation

The narrow passages of my nasal cavity maze limit the airflow through my nose, creating a ‘bottleneck effect.’ This narrowing causes a natural slowdown of my breathing by pressurizing the air. As a result, the airflow becomes more uniform and smoother.

By slowing down my breathing, I allow Nitric-Oxide buildup in my nasal cavity and regulation of Carbon-diOxide in my bloodstream. So, the limited airflow through my nose naturally assists in keeping me in balance.

Windpipe filtering

Once air leaves my nasal cavity, it continues through my windpipe, down toward my lungs. My windpipe, made of thick cartilage, is relatively broad and does not pressurize the air. Mucus coats the pipe, serving as the last filtering defense before the air enters my sensitive lungs.

Mouth inhaling

Filtration when mouth inhaling

When inhaling through my mouth, there are no fine hairs for filtering. In addition, my mouth cavity is broad, so particle trapping is not as effective as in my nose.

The saliva in my mouth works as a wet sticky filter, but it’s far less efficient than my nose mucus. As in my nasal cavity, particles and microbes which adhere to my saliva drain into my digestive system and undergo a sterilizing process.

Odor detection when mouth inhaling

Mouth inhaling allows a limited sense of smell. Odor-sensing in my mouth is by far weaker than my nose odor-sensing. So, naturally, when I attempt to assess an odor source, I approach it with my nose, not my mouth.

Nitric-Oxide treatment when mouth inhaling

Compared to my nasal cavity, there is hardly any Nitric-Oxide in my mouth cavity. As a result, I miss the disinfection and dilation functions of Nitric-Oxide when mouth inhaling.

Humidification when mouth inhaling

When mouth-inhaling, the air humidifies by evaporating my saliva. That contributes to better Oxygen absorption in my lungs. However, saliva has a few functions in my mouth, and its reduction due to evaporation may have adverse effects. For example, saliva protects my teeth from unwanted bacteria and decay. Some bacteria feast on food leftovers in the mouth and drill holes in the teeth; my saliva gives them a hard time and prevents damage. Unfortunately, I lose part of this dental protection by evaporating saliva when mouth-breathing.

Temperature regulation when mouth inhaling

Mouth inhaling results in poor temperature regulation. The evaporating saliva mentioned cools the air entering through my mouth.  However, if the temperature outside my body is lower than 37⁰ C  (98.6⁰ F), the cooling is a disadvantage because, optimally, air should get into the lungs at 37⁰ C  (98.6⁰ F) for good Oxygen absorption.

 Because the opening in my mouth cavity and the pipes leading to my lungs are broad, there is poor heat exchange. Therefore, the air reaching my lungs is at a lower temperature than my body’s, causing reduced Oxygen absorption.

Airflow regulation when mouth inhaling

When inhaling through my mouth, air goes down to my lungs through relatively wide openings and pipes. That causes air to swirl as I draw through my mouth. Conversely, airflow is slowed down, stabilized, pressurized, and smoothened when I inhale through my nose.

Nose exhaling

When exhaling through my nose, the air takes a reverse route from the lungs toward my nostrils. On its way through my nasal cavity, two reusing processes occur heat recycling and humidity recycling. These two mechanisms are fascinating and contribute to my breathing efficiency.

Heat recycling when nose exhaling

The air exiting my lungs is at a body temperature of 37⁰ C  (98.6⁰ F). On the way out of my body, the air’s heat exchanges on the surface of my nasal cavity structure, and the narrow maze absorbs the heat. This heat is ‘reused’ the next time I inhale, functioning as an efficient heat-preserving mechanism by recycling.

Moisture recycling when nose exhaling

The expelled air from my lungs is humid. On its way out of my body, it deposits moisture in my nasal cavity maze. This moisture is ‘reused’ on my next inhale, saving on my body liquids. Nose exhaling is efficient in preserving my body’s liquids by recycling.

Cleaning the filters when nose-exhaling

The flow of exhaled air blows away some of the particles trapped in the delicate hair filter around my nostrils. Other particles trapped by mucus and drying on the sides of my nose are the famous boogers I tend to remove using my index finger (in private).

Airflow when nose-exhaling

The narrow passages of my nasal cavity maze reduce the airflow, causing a natural slowdown in my breathing and contributing to keeping me in balance.

Mouth exhaling

Heat recycling when mouth exhaling

The warm air I exhale through my mouth passes through relatively wide pipes and a wide mouth cavity. So the air is expelled close to my body temperature, and there is hardly any recycling.

Important: Air exhaled from the mouth is warmer than air exhaled from the nose.

The way I sense nose/mouth air temperature difference

  1. I place the palm of my hand in front of my nose.
  2. Exhale air out of my nose at low and stable pressure.
  3. Place the same palm in front of my mouth.
  4. Exhale air with more or less the same velocity as when I exhaled through my nose.
  5. Compare the heat sensation of the air coming out of my mouth to that of my nose.

Now comes a tricky question. How can the same exhaled air warm my cold hands and cool down a hot cup of tea?

I need to have my hands very close to my mouth when warming them up by blowing on them. It’s the temperature difference that gives me a feeling of warmth. Air coming out through my mouth is closer to my body temperature, 37⁰ C  (98.6⁰ F), and my hands’ surface is normally colder at ambient temperature. The further my hands are from my mouth, the cooler the air will get to my hands due to heat exchange.

When blowing on the top of a hot cup of tea, the exhaled air is close to body temperature, 37⁰ C  (98.6⁰ F). The blown air is cooler than the liquid in the cup, which is close to boiling temperature. The movement of the blown air allows better heat exchange compared to the exchange with static air at ambient temperature.

Moisture recycling when mouth exhaling

As I exhale through my mouth, the humid air passes through relatively wide pipes into my mouth cavity. It hardly deposits moisture on the way out. Mouth exhaling denies nasal cavity moisture recycling.

Important: Air exhaled from my mouth is more humid than air exhaled from my nose.

The way I sense nose/mouth air humidity difference

  1. I start by holding one side of my smartphone screen close to my nostrils.
  2. Push air through my nose at a low and stable pressure, making the screen glass foggy.
  3. Turn the screen around so the opposite side is in front of my mouth.
  4. Push air through my mouth at the same low and stable pressure as I did through my nose, making the screen glass foggy.
  5. Visually compare the amount of fog deposited on each side of the screen.

Airflow when mouth exhaling

There is little air resistance when I exhale through my mouth due to wide pipes and a wide mouth cavity.

Important: From the above comparison, it’s evident that nose breathing has many advantages over mouth breathing.

Comparing nose and mouth breathing

The exceptions of mouth breathing

I use my mouth mainly to eat, drink, produce sounds, and kiss. Because nose breathing has so many advantages over mouth breathing, I try to avoid using my mouth as much as I can, both while inhaling and exhaling.  However, there are a few exceptions where mouth breathing is my preferred choice.

For instance, when facing a serious threat, I’m not concerned with microbes, pollutants, heat recycling, humidity recycling, and the like; these I can address after I get out of immediate danger. Instead, during an emergency, I breathe through my mouth to get into my lungs the extra air needed to power my muscles quickly and avoid getting hurt.

I exceptionally use my mouth for breathing when I:

  • Face an immediate emergency and need to escape or fight.
  • Produce sounds like when speaking, singing, or playing a wind musical instrument.
  • Make natural expulsions, like when I clear my throat, cough, yawn, burp, or hiccup.
  • Express nonverbal emotions, like when I vocally sigh.
  • Laugh(the ultimate breathing practice).
  • Exercise practicing specific breathing methods.

Mouth breathers

Unconsciously breathing through the mouth

Unconscious mouth breathing may stem from chronic nasal congestion or other bottlenecks in the nasal airways. It may also be a result of an emotional state.

In some older films, the character portraying a fool is often a mouth breather. However, times have changed; nowadays, it’s less of a stigma because so many people breathe through their mouths.

As mentioned earlier, it’s challenging to change how I breathe unconsciously. However, reforming unconscious mouth breathing to unconscious nose breathing is relatively easier than altering other aspects of my unconscious breathing.

Conscious mouth breathing

At times, I breathe intentionally through my mouth. For example, when I exercise or use specific breathing tools, mouth breathing may be a better choice to get the desired results. But I use mouth breathing sparingly because of its adverse effects.

In any case, I keep in mind that even fools seem smart when they keep their mouth shut.