Ragweed pollen levels are at their peak. Flu season is just weeks away. For many, a familiar tickle in the nose may soon be nearly impossible to escape. It’s time to explore the body’s most explosive reflex: the sneeze.
Scientifically known as sternutation, this involuntary reaction forcefully expels foreign particles like dust or dirt from the nose and upper airways. A single sneeze can propel up to 40,000 respiratory droplets nearly 30 feet at speeds of 35 mph. If the respiratory tract isn’t cleared on the first try, the brain triggers consecutive sneezes in rapid succession, usually in groups of two or three, to finish the job.
A sneeze doesn’t just spray droplets onto nearby surfaces. It also creates a “turbulent buoyant cloud” that can hang in the air for several minutes. While most sneezes harmlessly clear the airways of irritants, a sneeze from a sick person carries active viruses or bacteria, easily spreading infection to anyone nearby.
The biology behind the blast of a sneeze happens in seconds. When sensitive nasal nerve endings are irritated by particles or inflammation, the trigeminal nerve — the face’s main sensory pathway — alerts the “sneeze center” in the medulla oblongata at the base of the brainstem. The nerve endings fire, releasing a chemical messenger that triggers an immediate chain of responses: a reflexive inhale, closure of the eyes and, finally, closure of the epiglottis, a flap at the base of the tongue, to trap air inside the lungs. A split-second later, the diaphragm and chest muscles contract violently, the epiglottis pops open, and a blast of trapped air drives irritants out of your nose and mouth.
Although sneezes look alike, they generally fall into three distinct categories based on the underlying cause: allergies, infection, and physical triggers. Allergic sneezes — from exposure to allergens like pet dander or pollen — feature intense nasal itching, watery eyes, and a runny nose. The sufferer often sneezes repeatedly due to the ongoing release of histamine, part of the allergic response. An infectious sneeze, usually viral or bacterial, is accompanied by a thick yellow-green nasal discharge and systemic symptoms like fever and body aches. Sneezes from mechanical or chemical irritants like feathers or pepper are typically a “one-and-done” event. Once the offending particle is expelled, the nasal tickle and the need to sneeze immediately disappear.
Roughly one in three people can make themselves sneeze by looking at a bright light. Known as ACHOO syndrome, or autosomal dominant compelling helio-ophthalmic outburst, this genetic trait causes uncontrollable sneezing in response to sudden exposure to brightness — typically intense sunlight.
Sneezes should not be stifled. Pinching your nose or closing your mouth multiplies respiratory tract pressure up to 24 times compared with a normal sneeze, which can rupture blood vessels in the eyes and damage the eardrums. Instead of blocking a sneeze, contain it in a disposable tissue or the crook of your elbow rather than your bare hands.
To prevent sneezing fits, gently blow your nose and use saline spray to keep nasal passages moist. Minimize exposure to known triggers like smoke and perfume, and keep windows closed during peak allergy seasons. Running an air purifier and regularly replacing furnace and air conditioning filters will significantly reduce indoor dust and irritants.
Consult a health care provider if sneezing is accompanied by lingering cold symptoms or if it disrupts your sleep, work, or daily routine. You should also seek medical advice if you experience severe sneezing fits multiple times a day for several consecutive weeks.
Dr. Mary Jenkins, a contributor to the Herald and member of its board of directors, retired after nearly 40 years as a family practice physician in New York state.