Defense:
In general breathing through the nose has many advantages and is healthier.
When we breathe through the nose, the ait is filtered, warmed up and moistened. This is important, especially in very dry or cold places.
Moreover, the filtering that takes lace in the nose is a defence against virus and bacteria, pollution and allergens. There are some tiny hairs inside our noses called cilia. These work together with the mucous membrane to trap pathogens and reduce the risk of catching a cold.
Exercise:
When we perform moderate exercises, we will probably obtain a sufficient amount of oxygen mainly from our nose. As we increase the rhythm and intensity of our exercises, our body will need more oxygen. Of course, it is essential that we inhale a sufficient quantity of oxygen. In this case we can use mouth breathing, in order to absorb a greater quantity of air, and therefore of oxygen, but the frequency and depth of each breath are what really matters. When doing any form of heavy exercise most people tend to take faster and shallower breaths in an attempt to maximize the intake of oxygen. This is one of the most common mistakes, because by breathing superficially we are not using all of our lung capacity and this leads to a weaker performance and dizziness.
Health:
The nasal sinuses produce nitric oxide, also called nitrogen monoxide (NO), an essential componente for cardiovascular health, for regulating the blood circulation, optimize the immune system and even sexual health in men, because of its important role in the process of erection. Nitric oxide is also connected to other basic life functions, such as learning and memory, as well as being antifungal, antiparassitic and antibacterial.
Smell and memory:
Researchers of the Karolinska Institute in Stockholm, Sweden, and other institutions carried out an experiment, published in The Journal of Neuroscience.
Two dozen young and healthy volunteers, men and women, inhaled 12 different aromas from small vials which they brought to their noses.
Some of the smells were familiar, such as orange essence, whereas others were not. The subjects were told to memorize each aroma. They went through this process on two occasions.
On one side, they sat in silence for one hour immediately after smelling, with their noses closed in order to avoid nasal breathing; on the other side, they sat for one hour with tape over their mouth in order to avoid oral breathing. During each hour, their brains should have been consolidating the memories of the smells in the hippocampus, according to investigators hypothesis. After each hour, the volunteers were exposed to repeated and new smells, and then they were asked to determine whether they had smelled it before.
The men and women were able to recognize the smells much better if they had been breathing through their noses during the quiet hour.
Those who had been breathing through the mouth had a much fuzzier memory and gave more incorrect answers. As stated by Artin Arshamian, neuroscientist at the Karolinska Institute and main author of the study, “nose breathing improved the consolidation of memory”. Presumably, oral breathing was less effective because it bypassed the olfactory bulb, says Arshamian, and it didn’t initiate the same neural cascade.
We do not know if breathing through the nose can improve long-term memory when not connected to smell, or enhance cognition.
“However, I would not be surprised if it had a similar effect on memory in everyday life”, said Arshamian. He doesn’t think these hypothethical effects would be so big. But, he says, “considering that breathing has been used to change mental states for thousand of years, we still know next to nothing about respiration and brain function in humans.”
Children:
In children mouth breathing can represent a health risk, because it can alter the child’s development and the persistent effects of mouth breathing can be difficult to revert. Besides medum and long term complications can appear, such as facial and oral malformations, changes in posture, hearing problems, alterations in the sense of smell and taste, as well as sleep, speech or intellectual disorders and even problems in socialization.
There is wide evidence suggesting that children thaht breathe through the mouth are more likely to have difficulties at school, cry at night, grow at a slower rhythm, suffer from bad moods and develop bigger tonsils than children who breathe through their noses. When they grow up, mouth breathers are more prone to chronic fatigue.
Sleep:
If adults and children breathe through the mouth during the day, it is very likely that they also breathe through their mouth during the whole night. Mouth breathing at night, combined with an obstructed airway, are two symptoms directly related with sleep apnea and altered levels of carbon dioxide and oxygen in the blood.
If less oxygen can reach the brain, learning abilities and the capacity to concentrate at school become a problem for many children. In adults, chronic fatigue, tiredness and mental confusion are common symptoms connected to these problems.
Breathing through the mouth:
Mouth breathing is common in people whose nasal conducts are blocked or restricted. For example, a deviated septum or a small-sized one can lead the person to breathe mainly through the mouth instead of through the nose. However, breathing through the mouth can lead to hiperventilation. This, in turn, causes or worsens asthma symptoms, heart diseases and high blood pressure.