Sneezing is an involuntary reaction of our body. It involves making a expiration In view of the fact that sneezing is a reflex, it cannot be stopped either.

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Why do we sneeze?

Sneezing is caused by our own immune system. That's right, in short, sneezing is good. When our body detects the presence of micro-organisms in our respiratory tract, i.e. nose, throat or mouth, our body provides a sneeze to try to expel the unwanted invader.

These micro-organisms can be viruses or bacteria, related to diseases such as colds and flu, or particles such as pollen. In the latter case, allergy sufferers suffer from an exaggerated response from the body, which confuses pollen with disease-causing micro-organisms and tries to put it out, causing sneezing attacks.

How does sneezing occur?

The nose is the main route through which inhaled air enters and exits the lower airways. Due to its position, it has numerous functions. The narrow passages cause the inhaled air to flow with greater turbulence. This turbulence, in turn, increases the interaction between the airflow and the nasal mucosa (nose lining), allowing the exchange of heat and moisture and the removal ofsuspended or soluble airborne particles.

Sneezing is a physiological response to irritation of the lining of the respiratory epithelium of the nose. The process usually begins with the release of chemicals such as histamine or leukotrienes. These substances are manufactured by inflammatory cells, such as eosinophils and mast cells, normally found in the nasal mucosa.

Chemical release can be caused by respiratory infections from viruses or bacteria, allergens (substances that trigger allergic reactions, such as) or physical irritants such as smoke, pollution, perfumes and cold air.

The animation demonstrates what happens in our body during sneezing.

Allergies: immune system deceptions

Allergic reactions with the nasal mucosa require the presence of IgE (allergen-specific antibody). This leads to the leakage of fluid from vessels in the nose, causing symptoms of congestion and nasal dripping. In addition, nerve endings are stimulated, leading to itching sensation.

Finally, stimulation of the nerve ending leads to activation of a reflex inside the brain. The nerve impulse travels through the sensory nerves, controlling the muscles of the head and neck, and this leads to rapid expulsion of air.

The high velocity of airflow is achieved by increasing the pressure inside the chest with the vocal cords closed. The sudden opening of the cords allows pressurized air to flow back through the respiratory tract to expel the invader. However, in the case of influenza or other contagious diseases, such as COVID-19, this also allows spread because numerous viral particles arecontained in each drop of mucus expelled. That is why it is important to cover mouth and nose when sneezing.

Why do we sneeze when we look at light?

As we have said throughout the text, we sneeze due to microorganisms and allergies, but yet another type of sneezing, which arouses much curiosity: the sneezing that occurs when we look at the sun.

This type of sneezing is called photic reflex sneezing. This type of sneezing is caused by light stimuli, such as the sun's rays or even a very strong light bulb.

The photic reflex sneeze occurs because light suddenly reaches our eyes, it stimulates the optic nerve, which sends signals to the brain to contract the retina, protecting it from this light source. However, as the optic nerve is located very close to the trigeminal nerve, which transmits sensations from the face to the brain, confusion ends up happening. The trigeminal nerve also receives themessage from the optic nerve and understands that a nasal irritation is occurring, provides the sneeze.