Sneezing, like coughing, protects the airways. It is an unconscious, reflexive action that takes place independently of the human will. Unlike a cough, the stimulus to sneezing does not come from the mucous membrane of the airways, but only from the nasal mucosa.

The stimulus travels from the nose to the nerves in the medulla oblongata, from where again come the "commands" that involve the work of numerous muscles, which otherwise participate in breathing and coughing. Sneezing begins with a deep breath. After that, breathing stops completely, and the soft palate rises and closes the inner nostrils. At the same time, the muscles involved in exhalation tense up, and the pressure in the lungs rises. At one point the soft palate is lowered, the "door" for entering the nose is opened, through which a strong stream of air passes under strong pressure. The air from the lungs just passes explosively through the nasal passages, so this powerful jet allows all foreign and harmful substances to be removed from the nose.

Sneezing can be caused by many causes, and the most common is a cold or, as it is also called, runny nose, runny nose, sneezing. In addition to the headache, there is a slight swelling of the nasal mucosa, which becomes hypersensitive to stimuli. In such a case, sneezing can be caused by irritations that cannot cause any changes in a healthy nasal mucosa, eg a sudden change in temperature, stronger air flow, touch, smoke.

The sound of "ah-choo" can announce a more serious infectious disease. Sneezing occurs almost regularly in children with early measles; it is one of the first signs of flu as well as some other respiratory diseases. Because harmless sneezing can herald a more serious illness, the term "cheers" has emerged among the people, which is addressed to a person who rains with the desire to leave everything only to sneeze.
A common cause of sneezing is hypersensitivity of the nasal mucosa (allergy) to some substances that cause a strong stimulus in the nasal mucosa: pollen, odors, dust, gases, smoke. There are substances that almost regularly cause sneezing if they come in contact with the nasal mucosa: pepper, paprika, tobacco powder.

The irritation that leads to sneezing, and not strong enough, can be amplified by looking at a stronger light source, the sun, or a light bulb. Sneezing can also be caused by irritation of the external auditory canal, "ear digging", parasites in the nose. Sneezing can also be a hysterical phenomenon. It occurs more often in women, usually after family conflicts, in the workplace, due to unfulfilled desires. Hysterical sneezing can last for hours, weeks, or even months. Sneezing can be intentionally caused by gases and powders. Such agents are called sneeze gas and can cause salvos of dreadful sneezing. Sneeze gas, along with tear gas, belong to the group of irritant war poisons.