Your nose runs when you cry because your eyes and nose are physically connected. Tears do not only spill over your eyelids and down your cheeks. Some normally drain through tiny openings near the inner corners of your eyes and travel through ducts that empty into the nasal cavity.
When you cry hard, the system suddenly has much more fluid to handle.
Your eyes make tears all the time
Even when you are not sad, your eyes are covered by a thin tear film. Tears help lubricate the surface, wash away small particles, and support a healthy cornea.
Most of that fluid does not roll down your face. It drains through tiny openings called puncta near the inner corners of the upper and lower eyelids.
From there, tears enter small drainage channels and eventually pass through the nasolacrimal duct into the nose.
Crying overwhelms the normal drainage system
Emotional crying can produce far more tears than your eyes make during ordinary lubrication. Some spill over the eyelids, which is the part everyone notices.
A large amount can also travel down the normal drainage pathway into the nose. Once there, the tears mix with nasal mucus and make it thinner and more abundant.
That is why one emotional event can require tissues for two different parts of your face.
Your face has plumbing. Crying is what happens when somebody turns the faucet all the way up.
Why can your nose feel stuffy too?
The problem is not always just extra liquid. Strong emotions can affect the autonomic nervous system, which helps regulate blood vessels and secretions in the nasal lining.
Blood vessels in the nose may become more congested, and nasal glands can add their own secretions. That can make the nose feel both runny and blocked at the same time, an achievement that sounds contradictory until you have actually been crying.
Why does crying sometimes make you taste salt?
Tears contain water, salts, proteins, oils, and other substances. When tears reach your lips, you can taste some of that salt.
Tears that drain into the nose may also eventually reach the throat along with ordinary nasal secretions. That is another reason a long crying spell can leave your nose and throat feeling different afterward.
Do tears always drain into the nose?
Normally, yes, at least in part. The tear drainage system is working quietly all day. You usually do not notice because the volume is small.
If a drainage duct becomes blocked, tears may overflow onto the cheek more often. Blocked tear ducts are especially common in babies but can occur in adults too.
Why does your nose run when your eyes water for other reasons?
The same plumbing applies whether the tears came from emotion, onions, cold wind, eye irritation, or another trigger. More tear production means more potential fluid entering the nose.
That is why cutting onions can leave you wiping both your eyes and your nose. The onion started with chemistry, then your drainage system joined the production.
Crying does not somehow make your nose forget its job. It makes the normal eye-to-nose drainage system suddenly very obvious.
The same body systems connect with Why do onions make you cry?, another everyday effect with its own underlying mechanism.
And that’s the short explanation.
Related explanations: Why do onions make you cry?, Why do we sneeze?, and Why do bug bites itch?