My medical knowledge is a bit rusty by twenty years but in ELI5 terms… a sneeze uses involuntary muscles… ie you consciously don’t have control over your body sneezing once it is in the middle of a sneeze. Your body in its use, it’s trying to forcefully expel a foreign object substance, dust, dander, etc… and so your entire body is triggered, to sneeze… involuntarily and without a control mechanism.
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