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Why is it that when I sneeze, I almost always do so twice?

Geoff Broughton, Abingdon-on-Thames, Oxfordshire, UK

Only twice? My wife always releases a volley of six loud sneezes. There is palpable tension in the room if numbers five and six are momentarily delayed. How can her nasal system reliably count to six while under such strain?

Taylor Rey, Suwanee, Georgia, US

Almost every time I sneeze, I do so seven times in a row. The sneezes come in fast succession, but occasionally the last one lags behind by a few seconds.

Harsha Kariyawasam, Royal National Throat, Nose and Ear Hospital, London, UK

Sneezing is an underappreciated upper-airway event. It is a critical airway protection mechanism that prevents the entry and depositing of potentially hazardous agents into the nose.

It is normal to sneeze two or three times a day. This indicates that our nasal defences are active and working. Frequently, one sneeze isn鈥檛 enough, so it is promptly followed by another to ensure that any inhaled threats are fully expelled.

In conditions such as hay fever or rhinitis, there is often irritation of the sensory nerves of the nose such that the sneezing reflex activation threshold is lowered. This results in anything from allergens to temperature change and even strong smells activating a sneeze.

The brain doesn鈥檛 regulate or 鈥渃ount鈥� sneezes, as sneezing is driven by a neuronal/muscular reflex. It is an involuntary act.

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