Tears do not simply evaporate off the front of your eye. Every blink spreads a fresh film across the surface, then sweeps the used fluid toward the inner corner, where a small piece of plumbing carries it away. When the system works, you never think about it.
You think about it when it stops. Tears spill over the lower lid on a dry day with no wind, the inner corner feels puffy, or one eye alone weeps and crusts. Those are usually signs of a drainage problem rather than a problem with tear production.
Here is the route tears take, why blockages happen at very different ages, and what an eye doctor is looking for when the pipe backs up.
The route out of your eye
Look closely at the inner corner of your eyelid and you can see a pinhole opening on both the upper and lower lid margin. Those are the entrances. From each one, a short channel runs inward and the two channels merge before emptying into a small reservoir called the lacrimal sac, which sits just beside the bridge of your nose.
From the sac, the nasolacrimal duct heads downward through a bony canal and opens inside your nose, low and toward the back, under a shelf of tissue in the nasal wall. In other words, the far end of your tear drain is the same air space you breathe through.
Blinking does the pushing. The muscles that squeeze your lids shut also compress and release the sac, creating a gentle pumping action that moves fluid along. That is one reason people who blink poorly, or whose lids sit loosely against the eye, often have watery eyes even with a wide-open drain.
Why a good cry makes your nose run
Emotional tears arrive faster than the drain can clear them. Some spill down your cheeks, but a large share still goes where all tears go, which is straight into your nose. Add the extra fluid to the mucus already there and the result is a runny nose.
The same pathway explains the strange taste some people notice after certain eye drops. A drop placed on the eye can drain through the duct and reach the back of the throat within a minute or two. It is also why doctors sometimes suggest gently pressing the inner corner after using a drop, which slows that escape.
When the drain is blocked from birth
Many babies are born with the lower end of the duct still covered by a thin membrane that has not opened. The usual picture is a baby whose eye waters constantly from the first weeks of life, with a build-up of yellowish discharge and lashes stuck together after sleep. The eye itself typically looks white and comfortable, and the baby is not bothered.
The reassuring part is that most of these blockages open on their own during the first year. Pediatricians and eye doctors often teach parents a specific massage technique over the tear sac and explain how to clean the lids. That instruction should come from the clinician who examines the child, since technique matters and other conditions can look similar.
Book sooner rather than later if the eye turns red, if the lids swell, if a tender lump appears beside the nose, or if the baby seems in pain or feverish. Constant watering that has not settled by the child's first birthday is also worth a conversation, because there are procedures that help when nature does not finish the job.
Blockages that show up later in life
In adults, the duct usually narrows rather than never opening. The lining thickens with time, and the passage gets tighter, which is part of why watery eyes become more common with age. Repeated infections, chronic nasal inflammation, previous facial fractures, nasal surgery, certain medications and, less often, growths in the sac can all contribute.
The classic complaint is a single eye that runs outdoors, in wind, or in cold air, and blurs the vision until you dab it. Many people assume it is dry eye and reach for lubricating drops. It is worth getting checked, because the answer depends entirely on where the narrowing sits.
When a blocked duct becomes an infection
Standing fluid invites bacteria. When the lacrimal sac becomes infected, the condition is called dacryocystitis, and it has a recognizable look: a red, swollen, tender bump on the side of the nose just below the inner corner of the eye, often with pus and heavy tearing.
An acute case can come on within a day and can be genuinely painful, sometimes with fever. That deserves same-day medical attention rather than a wait-and-see approach, because infection in this area sits close to the tissues around the eye. A chronic version is quieter, showing up as ongoing watering and repeated low-grade flare-ups over months.
What an eye doctor checks
An exam for a watery eye is more detailed than most people expect. The doctor looks at how the lids sit against the eyeball, whether the drainage openings are in the right position and open, and whether the tear film itself is healthy, since a dry, irritated surface can trigger reflex flooding that mimics a blockage.
They may press over the sac to see whether fluid comes back out, and they can flush the system with sterile fluid to find where it stalls. That is what turns a vague complaint about watering into a specific answer.
Common questions
Can a blocked tear duct cause dry eye?
Not directly, since blockage affects drainage rather than production. But a poor-quality tear film and a slow drain can exist together, and both can leave the eye irritated and watery at the same time.
Are watery eyes always a duct problem?
No. Allergies, wind, lid position, eyelash problems and a dry ocular surface all cause tearing with a perfectly open duct. Sorting out which one you have is the reason to have it examined.
Can I flush my own tear duct at home?
No. Irrigation is done with sterile equipment by a trained clinician. Home attempts risk injury and infection, and they will not tell you where the narrowing is.
A watering eye is easy to shrug off, and it is often minor, but it can also be the first hint of a blockage or an infection that responds better when it is caught early. If one eye has been running for weeks, it is worth having someone look at the whole pathway. You can search for an eye doctor in your network and get it sorted out properly.