Does a Sneeze Mean Disease?

Got a cold? Are you allergic to something? These seem to be routine questions any time I sneeze, but they always leave me feeling somehow falsely accused—I have neither a cold, nor allergies (as far as I can tell) and yet, there's this assumption that if there's a sneeze, it must be one or the other.

That's one of a number of myths surrounding the sneeze. Other myths (or are they facts?) about sneezing are that you cannot keep your eyes open during a sneeze; that your heart stops when you sneeze; that looking at a bright light can trigger a sneeze, and that rubbing the bridge of your nose can prevent it.

And then there are what might best be called superstitions, for example: "Sneeze before seven, company before eleven;" or "Always say 'God bless you' when you sneeze, to keep the devil from flying down your throat." These superstitions attach significance to the number of times you sneeze, when it happens, or various blessings that should accompany a sneeze.

So there is plenty of advice and folklore built around sneezing. For such a common reflex—found throughout the animal kingdom—it is surprising how little is known about it. Let's take a look at what we do know.

What is a sneeze?

The medical term for a sneeze is "sternutation" (though I've never heard that term used!), a complex reflex involving nerves in the nose that detect swelling of the nasal membranes, particles of a certain size, or substances to which you are allergic.

Particularly good stimulators of sternutation are pepper, cold air, and dust. These triggers send messages to the throat, chest and abdomen to contract in a particular sequence to forcefully rid the nasal passage of its contents. For unknown reasons, perhaps as protection from flying particles, the muscles of the face, including the eyelid muscles that briefly close the eyes, are also in the loop. The end result is that the offending agents in the nasal passages are forcefully expelled.

And forceful it is: Particles exiting the nasal passages have been clocked at more than 100 miles and hour. The contents of the upper airways and mouth also contribute to the expelled material—in fact, while dogs and cats (and perhaps other animals) sneeze primarily through their noses, most of the expelled material during a human sneeze departs by way of the mouth. That's why covering both your mouth and nose when sneezing is important.

Sneezing in disease

The underlying conditions most associated with sneezing are allergies or infections. Dust, tree and grass pollen, dander (often from pet hair) and molds are among the most common allergic triggers.

Viruses that inhabit or invade the nasal passages can cause swelling of the membranes, increased mucus and runny nose. They are much more common triggers of sneezing than bacteria, fungi or other infections. In fact, the virus that classically causes the common cold get its name ("rhinovirus") from its tendency to take up residence in the nose—the prefix "rhino-" comes from the Greek rhis, meaning "nose." If you have a cold as the cause of your sneezing, the particles projected into the environment may be teeming with potentially infectious viruses.