Physics
Why does crying make your nose run?
Quick fact
Tears drain from the eyes through the nasolacrimal ducts, which empty into the nasal cavity, mixing with nasal mucus and causing the nose to run.
Why this is interesting
Your nose doesn't produce extra fluid when you cry—it's actually your tears draining down a tiny duct in your eye corner, and they mix with mucus in your nasal cavity, creating that familiar runny nose.
Read the full explanation
Understanding Why does crying make your nose run?
The tear duct (lacrimal punctum) in the inner corner of your eye collects tears and channels them through a tube that ends in the nasal passage. When you cry profusely, the volume overwhelms the system, and the overflow runs out your nose.
A deeper explanation
This is why you taste tears at the back of your throat—they're literally traveling from your eyes to your nasal cavity and down to your pharynx. The composition of emotional tears differs from reflex tears (like from smoke): they contain stress hormones and natural painkillers (leucine-enkephalin), suggesting crying has a chemical purpose of emotional regulation. The runny nose is just a plumbing side-effect, but it's a perfect demonstration of how your body's drainage systems are interconnected—your eyes, nose, and throat are all part of one continuous passage, and when one floods, the others get wet.