By Korin Miller
Today in “bodily phenomena you know can happen but have no idea why”: Why do your eyes water when you yawn? We’re just going to get this out there right now…doctors aren’t entirely sure. “Nobody really knows the true mechanism behind this,” 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, tells SELF, adding that experts haven’t fully sussed out why people yawn in the first place.
That said, doctors have some solid theories on what’s behind this yawning/tearing experience, including what it might mean if it doesn’t really happen to you. To understand those speculations, we first have to dive into what your tears are at a basic level.
Your tears consist of three unique layers that come together to help moisturize your eyeballs.
A mix of fatty oils, water, and mucus create a tear film that keeps the surface of your eyes smooth and attempts to protect you from irritants and infection-causing pathogens, according to the National Eye Institute (NEI).
That oily layer prevents your tears from evaporating too quickly. Your Meibomian glands, which are located under your eyelids, pump out the oil for this portion of your tear film. There’s another layer consisting of water and water-soluble proteins, both of which come from the lacrimal glands under your eyebrows. This layer helps nourish your corneas (the dome-shaped outer surface of your eyes) and conjunctiva (the mucous membrane over part of your eyes and the insides of your eyelids). There’s also a mucous-based layer that gloms onto the water in your eyes so they stay moist.
This special mixture spreads across your eyes when you blink, and it also creates tear droplets that leak out when you cry or yawn. Specifically, “When your eyes tear up, the watery layer is overproduced,” Zeba A. Syed, M.D., a cornea surgeon and assistant professor of ophthalmology at Wills Eye Hospital, tells SELF.
Tearing up when you yawn probably comes down to how you contort your face when your mouth is wide open.
As you know, when you yawn, your face scrunches up and you usually either close your eyes or squeeze them until they’re practically shut. This puts pressure on the lacrimal glands under your eyebrows, which can cause them to produce more of that watery layer of your tears, Vivian Shibayama, O.D., an optometrist and contact lens specialist with UCLA Health, tells SELF. Bam—now your eyes runneth over.
Another factor here: Your tears normally drain out of little ducts at the inner corners of your eyes, the NEI says. But squeezing your facial muscles during a yawn can temporarily close off these ducts, keeping those tears in your eyes a little longer than usual. “All that extra fluid has no place to go,” Dr. Massaro-Giordano says, so you tear up. “Then, when you open your eyes, the extra tears find their way to the drains with the next couple of blinks.”
Not everyone tears up when they yawn, though. Even if it’s normal for you, it might not happen every time.
How often this happens to you could depend on a few things, including your anatomy. If your tear ducts are pretty large, your eyes may be able to drain those excess tears as you yawn, Dr. Massaro-Giordano says.
You also might not experience this phenomenon if you have dry eyes. This can happen because you’re in a specific situation, like being on a windy beach that strips moisture from your eyes. It can also happen more persistently if something makes your tear film regularly evaporate too quickly, like working at a computer all day, so you blink less often to replenish your tear film. Or you might experience dry eye because something is stopping your eyes from producing enough of a tear film to begin with, such as taking decongestants or another medication that can lower your tear production. All of this can cause symptoms like dryness that prevents your eyes from tearing up when you yawn, stinging, burning, pain, and more. Some people even have a specific condition called aqueous-deficient dry eye, meaning there’s not enough of that watery layer in their tear film, which could make it especially likely that your yawns are tear-free.
Interestingly enough, dry eye can also cause excessive tearing as your eyes overcompensate to address the dryness. If that happens, you might tear up basically all the time, including when you yawn.
So, your eyes might water when you yawn. They might not.
Either way, it doesn’t mean something’s wrong with your eyeballs as long as you’re not experiencing any strange eye symptoms like really uncomfortable dryness, irritation, or pain. Usually, it’s just one of those things.