The Real Reason Yawning Makes Your Eyes Water
Yawning seems like such a simple act. Your mouth opens, maybe your eyes close, and you take a deep breath. Your soul might not escape from your body when you forget to cover your mouth, but yawning might make your eyes water. Researchers are still studying the underlying reasons that this happens.
Most people have heard that yawning is contagious. The idea is that if you see someone else yawn, you will reflexively yawn also. Another theory is that you yawn because your brain is in need of oxygen. While there's some research to support contagious yawning, doctors say that the idea that you yawn when your brain needs oxygen just isn't true (via Cleveland Clinic). What researchers do know is that yawning helps the brain regulate its temperature. What might seem like a contagious yawn is probably just the result of two people being in a similar environment and reacting to the ambient temperature.
Watery eyes, happy brain?
Researchers have also found a possible connection between yawning to cool the brain and watery eyes. The tears themselves may help move heat away from the brain and out of the head (via Healthline). Your facial muscles that tighten when you yawn could also play a role by squeezing the glands that make tears, essentially forcing your eyes to water.
It's possible that underlying health issues such as dry eye syndrome, allergies, or even taking certain medications could be causing those teary-eyed yawns (via Mayo Clinic). Dry eye syndrome actually makes your eyes produce more tears than normal, because they don't have enough moisture to keep them protected from irritants. Most common causes of watery eyes can be treated once they're properly diagnosed. Even too much yawning itself may indicate an underlying condition that a doctor might be able to treat. In most cases, both conditions are normal and don't require medical treatment.