Through the sneeze the expulsion of irritating or contaminating substances occurs from the nasal cavities and from the mouth.
More precisely, with the sneeze a sort of aerosol is emitted, composed of fluids (like droplets of saliva), mucus, epithelial residues, white globules and infectious and / or irritating substances, dispersed in respiratory gases.
All these substances are enclosed in tiny wet particles, improperly referred to as droplets of saliva. It is estimated that an average of 20, 000 to 40, 000 droplets are emitted for each sneeze, more correctly referred to as droplets from Flugge .
These droplets are so small and light that they evaporate, leaving their components in the air for a long time. Among these, the presence of infectious substances explains the high contagiousness by air of some diseases transmitted with sneezing, such as the flu or the cold (viral rhinitis).
Placing the hands in front of the nose when sneezing limits the spread of these droplets in the air, preventing the spread of infectious diseases by air. However, the problem of transmission is created through the shared use of handles or objects of common use manipulated by the patient after having sneezed, sheltering with his hands.
For this reason, some claim it is more correct to bring the forearm to the mouth, rather than the hands, when sneezing.
