Unfortunately, though, your attempt at common courtesy could leave you with a rare and dangerous medical condition. That's what happened to a 34-year-old man in England, according to a case study in the British Medical Journal, when he tried to stifle a sneeze by closing his mouth and pinching his nose. He felt a popping sensation in his throat, his neck began to swell, and he even had trouble swallowing and talking. After spending seven days in the hospital, where he was fed with a nasogastric tube, he made a full recovery—but why was he there in the first place?

When mucus, an allergen, or an object like an insect gets into our nose, the body's instinct is to get rid of it immediately, via a sneeze. The diaphragm and the muscles between our ribs contract to expel whatever's in our nose. It's an automatic (and largely uncontrollable) reflex, designed to keep our airway open. Here's a visual that explains what really happens when you sneeze.

A sneeze is also very powerful. Depending on the size of your nose and your lung capacity, the force reaches more than 100 miles an hour! But holding the nose, or closing the mouth, means that all that air can't escape, so it has to go somewhere else, which could cause unexpected damage.

"If you try to suppress the velocity of air coming up from the lungs, then you could cause damage to the middle ear, which is where the hearing bones are," cautions Jeffery Gallups, MD, founder and director of The ENT Institute in Atlanta. The force of the air being pushed at high speed into the eustachian tubes can affect the eardrum and the small bones that vibrate when we hear sounds, Cleveland Clinic explains. Another (though exceedingly rare) possibility is a spontaneous pharyngeal rupture, which the unidentified British man experienced. His contained sneeze ruptured his throat and left air bubbles in the soft tissue of his neck and chest.

"Halting sneeze via blocking nostrils and mouth is a dangerous maneuver," the authors of the case study wrote, "and should be avoided, as it may lead to numerous complications." If you have an underlying condition, including osteoporosis or an existing brain aneurysm, other complications could arise from an uninhibited sneeze.

Since there's no surefire way to ward off a sneeze, go ahead and let it rip—but do consider those around you. Sneeze into a tissue or the crook of your elbow, dispose of the tissue immediately, and wash your hands to get rid of germs. Don't miss these 12 more weird facts you never knew about sneezing.