Aaa-Choo! What happens to your body when you sneeze?

Posted on 31 August 2017

You can’t do it on demand and you can’t do it in your sleep. But it won’t make your eyes pop out of your head either. Researchers say sneezing is a way of “resetting” your nasal cavities. And if you want to be technical, it’s called sternutation.

When you sneeze, your respiratory, nervous and muscular systems all work together. “This involuntary process often starts with the release of chemicals, such as histamines, that are manufactured by mast cells in the mucus of your nose,” says Dr Jibril Ayodele, an ENT surgeon at Mediclinic Ermelo. “Release of these chemicals is triggered by anything from viral respiratory infections and allergens to smoke, pollution, dust, pollen and pepper.”

  1. An irritant enters the respiratory epithelium that lines your nose.
  2. This stimulates the trigeminal nerve (the 5th cranial nerve) to send a message to the “sneezing centre” in your brain.
  3. Your body’s “sneezing centre” is found in the lateral medulla. It triggers the outward (efferent) phase of your sneeze.
  4. Brainstem motor nuclei make your eyes close.
  5. You breathe in deeply.
  6. Your vocal cords, uvula and soft palate close.
  7. Your respiratory muscles contract, making pressure build up inside your chest.
  8. Once a high enough pressure is reached, your vocal cords, uvula and soft palate suddenly open in response.
  9. The release of intra-thoracic pressure creates an explosive air flow through your nose and mouth.
  10. Up to 40 000 little droplets of saliva and mucus are ejected at a speed of 100 metres per second.

Sneeze illustration

What does mucus mean?

If you have a runny nose and your mucus is thin and clear, it suggests hayfever. If it is green, brown or yellow, it means the white blood cells in your body are working hard to fight an infection and you should see your doctor.

4 truths about hayfever

  1. Seasonal hayfever occurs in spring and summer and is triggered by sensitivity to pollens from grass, trees and weeds. Perennial hayfever occurs year-round and is triggered by sensitivity to dust mites, pet hair, mould, cigarette smoke, cosmetics and cleaning products.
  2. Symptoms include a stuffy nose, itchy nose and eyes, puffy eyelids, sneezing and coughing.
  3. To avoid triggers, close car and house windows during high pollen seasons; wear sunglasses outdoors; wash your hands after petting animals and consider mite-proof bedding.
  4. You can control the symptoms with decongestants and anti-histamines.



Published in Healthy Life

In the interest of our patients, in accordance with SA law and our commitment to expertise, Mediclinic cannot subscribe to the practice of online diagnosis. Please consult a medical professional for specific medical advice. If you have any major concerns, please see your doctor for an assessment. If you have any cause for concern, your GP will be able to direct you to the appropriate specialists.

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