Dear Dr. Rabin:
Tell me this: Why do I sneeze every time I pluck my frickin’ eyebrows? —LizBeth

You must really go through the Windex. I don’t pretend to understand the high price women pay for beauty, but the thought of you holding a pointed object near your face while you repeatedly sneeze gives me the shivers. Could your body be trying to tell you that ripping individual hairs from its skin, one by one, is simply a bad idea? Shaving your brows is one option, I guess, though a sudden sneeze at the wrong moment might have more, shall we say, asymmetric ramifications.

The sneeze itself is a very odd thing. Perhaps the most violent reflex in the body—with the exception of the reaction to being sneezed upon—it is a completely involuntary expulsion of air following an unexpected stimulation of, most often, a nasal membrane. Although the seemingly obvious purpose is to blast an irritant out of your nose, the logic falters when you notice that we mostly sneeze out of our mouths. By we, I mean human adults. Any pet owner or parent can testify from sticky experience that dogs, cats and babies definitely sneeze out of their noses.

The trigger for the reflex can be likened to an itch, and is frequently an irritant like dust, pollen or cold air contacting the nasal mucosa. Although scratching the itch could be done with a finger, evolution has chosen instead a cascade of sudden inhalation, extreme muscle contraction and forceful exhalation. Immediately following the discharge, histamine is released to turn on a stream of mucous in an attempt to wash out the offending particle. So why in the world would the tweezing of an eyebrow hair cause this spontaneous cavalcade of activity? The answer is found, LizBeth, in the layout of the nerves of your face.

The trigeminal nerve, or fifth cranial nerve, has functions that include both muscle movement and sensation. One of its three branches, the ophthalmic, monitors and reports to the brain everything that happens in the nasal passages. But, as fate would have it, the same wiring relays messages from the skin of the forehead, eyelids, and a few other nearby locations. This overlap—worse in some people than in others—can confuse the brain into delivering a sneeze when a more appropriate response would be: “Cheese and Rice! Quit ripping out my hair!”

Another example of these crossed wires is known as photic sneezing, or sneezing caused by looking at the sun or other sources of bright light. Apparently, the reflexive sudden squinting of the eyes and forehead also sends a flash of signals through trigeminal nerve in the same manner as, say, pulling a nose hair. This short-circuiting seems to have a genetic component, as only about 25 percent of the population is compelled to sneeze when looking at bright lights.

Since your question was fairly straightforward and easily answered, there is room here to address some of the many myths about sneezing that get passed around like viruses. An elementary school favorite says that your eyes will pop out if you manage to keep them open when you sneeze. Another contends that your heart stops every time it happens. Though it would be a strange talent to keep your eyes open when you sneeze, and your heart may indeed momentarily slow, neither legend is true. Regardless, I plan to continue carrying an emergency pepper packet in case I find myself at a matinée of License to Wed. Ripping my eyes out or stopping my heart would be welcome relief.

Stifling a sneeze is a common practice among teenagers (for fun) and introverts (for social camouflage), despite essentially fictional warnings against bursting a brain aneurysm. Still, it’s not a good idea. Holding back a nearly-inevitable snot rocket may send microbe-laden fluid up the eustachian tube and cause an ear infection—or worse, in rare cases, the sudden rise in pressure can rupture the ear drum. Best advice: Just admit defeat and let it fly.

But cover your mouth. Sick or not, that sneeze can send infectious droplets flying at hurricane-force speeds of 100 miles per hour. Catch the mist in the crook of your arm or in a tissue, if possible, rather than your hands—unless, of course, there’s a make-up mirror in front of you. Sadly, there isn’t much to be done to prevent post-tweezing sneezing, though a brisk pre-pluck rub of the entire eyebrow area may help. Should it become unbearable, however, a vacation from epilation may be necessary. Worry not: There are worse things in life than looking like Brooke Shields.