A sneeze is a reaction in the body that suddenly presses air out of lungs so it flows out through the mouth and nose. Air and mucus (the liquid found in the nose) are forced out quickly. Sneezing often happens after breathing dust or other small things that irritate the membranes in the nose. The function of sneezing is to clean the space in the nose by removing the mucus and irritating things. Sneezing is mostly involuntary, which means that it happens without trying.

A sneeze consists of a deep inward breath that fills the lungs, a closing or partial closing of the throat, and a sudden increase in pressure in the lungs that forces air out. This increase in pressure is a result of muscles near the lungs that contract (tighten and shorten). When people sneeze, their eyes also close. Sneezing never happens during sleep because reflex signals do not pass to the part of the brain that causes muscles to move. The speed of the air from sneezing is about 150 kilometers per hour or more.^[1]

Many animals sneeze, including human beings, cats, dogs, chickens^[2] and iguanas.^[3] When a person sneezes, many small drops of saliva and mucus blow out from the nose and mouth. These tiny drops usually have viruses and bacteria inside. Some of these are germs, which can make other people sick. To keep this from happening as much, it is common to block the sneezed air with something like cloth or tissue to catch the drops. It also helps to move away from other people, go outside, or face away.

A common thing to say to people when they sneeze is "Bless you!", or sometimes "Gesundheit!" (from German, meaning "Good health"). There is a story that the blessing started with Pope Gregory VII (540–604AD). He said a blessing might stop people from getting the bubonic plague which was killing people in Rome at the time.^[4] There is a myth that when you sneeze, your heart and all internal organs stop functioning.^[5]

The sound of a sneeze is written as "achoo!" in English. Other languages write it differently. For example, in Swedish it is "atjoo!", in French it is "atchoum!" and in German it is "Hatschi!".

• Cough
• Hiccups
• Yawn