Here's Why Your Eyes Water When You Yawn

Yawning is contagious; you might even be yawning while reading this. Whether or not yawning is accompanied by tears, however, doesn't actually depend on how tired we are, even though it might feel like that sometimes.

In fact, as Mina Massaro-Giordano, M.D., co-director of the Penn Dry Eye & Ocular Surface Center and a professor of clinical ophthalmology at the University of Pennsylvania, admitted to Self, doctors don't completely understand why we yawn in the first place. Likewise, they don't know why our eyes sometimes water when we yawn, too. But they do have an idea. 

First off, it's worth noting that tears, which consist of fatty oils, water, and mucus, have an important function — to keep the surface of our eyes smooth and to protect them from irritants and anything else that might cause an infection, according to the National Eye Institute (NEI).

The lacrimal glands, which are tucked just under your eyebrows, produce water and water-soluble proteins that help nourish your eyes. A mucus-based layer attaches to the water in your eyes to keep them moist, too. This mixture spreads across the eyes when you blink, but it also creates tears whenever you cry or yawn.

As Zeba A. Syed, M.D., a cornea surgeon and assistant professor of ophthalmology at Wills Eye Hospital, explained to Self, "When your eyes tear up, the watery layer is overproduced."

When we yawn, we tend to scrunch our faces up and either close or squeeze our eyes tightly, which puts pressure on our lacrimal glands and causes them to produce more tears. They usually drain out of little ducts at the corners of our eyes, but when we squeeze our facial muscles, they can temporarily close. 

As Dr. Massaro-Giordano notes, "All that extra fluid has no place to go. Then, when you open your eyes, the extra tears find their way to the drains with the next couple of blinks."

Either way, there's nothing to worry about if your eyes are tearing up when you yawn — or if they're not. As long as there aren't any accompanying symptoms, such as excessive dryness, irritation, or pain, it's totally normal.

As optometrist Cheryl G. Murphy wrote in Huffington Post, "It's not sad, it's just science."