There's every good reason in every country in the world to promote education around sneeze etiquette, to suggest people stay home when they're sick, to not take their illness to school,to work.

VOA: standard.2009.04.28

You sneeze because you've got all these germs inside you and your body wants to get the germs out, so you sneeze.

你打喷嚏，因为细菌在你体内,你的身体想把他们赶出去，所以你打喷嚏。

耶鲁公开课 - 心理学导论课程节选

From this point of view then, the reason why you sneeze when you have a cold is that your cold the cold virus is using your body as a tool to replicate itself.

从这个角度看，感冒时打喷嚏是因为,感冒病毒用你的身体繁衍后代。

耶鲁公开课 - 心理学导论课程节选