Why do people blow there nose when they cry?

Perhaps the first question is ask why we cry. Without an extensive knowledge of the physiology one could make a guess that pain to areas of the face when confronted with natural irritants would favor those that could induce a flushing of both eyes and nose to clear irritant from face.

This evolutionary response to pain carried over to emotional pain when we evolved to have complex emotional response to feelings.

So the pain emotionally is exhibits the same response it did to protect us from irritants in nature with both eye and nose flushing out.The two reactions are so wired together in us over time they now are areactionary pair.In reverse , try to sniff an onion without crying also.

I am sure someone who studied anatomy can give the mechanics of how it happens.

But this is my best guess as to why evolutionary speaking.