It’s a common experience: you open your mouth wide for a big yawn, and suddenly, tears well up in your eyes. But have you ever stopped to wonder, “Why Do My Eyes Water When I Yawn?” It’s one of those peculiar bodily functions that many of us experience without truly understanding. While it might seem straightforward, the exact reason behind this phenomenon is more nuanced than you might think, and even experts are still piecing together the complete picture.
To unravel this watery mystery, we need to delve into the fascinating world of tears and the mechanics of yawning. Let’s explore the current scientific understanding of why yawning often leads to a surprising rush of tears.
The Complex Composition of Your Tears
Before we connect yawning to tearing, it’s helpful to understand what tears are made of and their crucial role in eye health. Tears aren’t just salty water; they are a sophisticated fluid with three distinct layers, each playing a vital part in maintaining eye moisture and protection.
These layers combine to form the tear film, a crucial coating that keeps the surface of your eyes smooth, clear, and shielded from irritants and infection-causing agents, as highlighted by the National Eye Institute.
- Oily Layer: This outermost layer, produced by Meibomian glands located in your eyelids, prevents tears from evaporating too quickly. Think of it as a sealant that keeps your eyes from drying out.
- Watery Layer: The middle and thickest layer, originating from the lacrimal glands situated under your eyebrows, is composed of water and water-soluble proteins. This layer nourishes the cornea (the clear front surface of the eye) and conjunctiva (the membrane lining the eyelid and covering the white part of the eye).
- Mucous Layer: The innermost layer, closest to the eye surface, consists of mucus. This layer helps the watery layer spread evenly across the eye, ensuring consistent moisture and lubrication.
This intricate mixture is spread across your eyes every time you blink, maintaining hydration and flushing away debris. And, as you know, this system can also produce a more significant outpouring of tears when you cry or, indeed, when you yawn. As Dr. Zeba A. Syed, a cornea surgeon at Wills Eye Hospital, explains, “When your eyes tear up, the watery layer is overproduced.”
The Yawning Link: Facial Contortion and Tear Production
The most likely explanation for why yawning triggers watery eyes lies in the physical actions your face undergoes during a yawn. Consider what happens when you yawn: your mouth opens incredibly wide, your face muscles contort, and you often squint or close your eyes tightly.
This facial contortion is key. When you yawn, the scrunching and squeezing of your facial muscles put pressure on the lacrimal glands, those tear-producing glands located under your eyebrows. This pressure can stimulate the lacrimal glands to produce an excess of the watery component of tears, as Dr. Vivian Shibayama, an optometrist at UCLA Health, describes. The result? Your eyes begin to water.
Furthermore, the muscles tightening around your eyes during a yawn can also affect the tear drainage system. Normally, tears drain away through small ducts located in the inner corners of your eyes, as the NEI notes. However, the squeezing action of your facial muscles during a yawn can temporarily constrict or even close these tear ducts.
Dr. Mina Massaro-Giordano, co-director of the Penn Dry Eye & Ocular Surface Center, clarifies, “All that extra fluid has no place to go,” leading to the welling up of tears. Once you relax your facial muscles and open your eyes fully after the yawn, the tear ducts reopen, and “the extra tears find their way to the drains with the next couple of blinks.”
Why Doesn’t Everyone Tear Up Every Time They Yawn?
Interestingly, not everyone experiences watery eyes with every yawn, and even those who do might not tear up consistently. The frequency of this phenomenon can vary depending on individual factors, including your unique anatomy.
One key factor is the size of your tear ducts. If you naturally have larger tear ducts, your eyes may be more efficient at draining away the excess tears produced during a yawn, as Dr. Massaro-Giordano points out. In such cases, the temporary blockage caused by yawning might not be enough to cause noticeable tearing.
Other subtle anatomical variations or differences in muscle contraction strength during a yawn could also play a role in why some people are more prone to yawn-induced tears than others.
The Unsolved Mysteries of Yawning and Tearing
While the pressure on lacrimal glands and temporary blockage of tear ducts offers a compelling explanation for why eyes water when yawning, it’s important to remember that the exact mechanisms of both yawning and tear response are still not fully understood. As Dr. Massaro-Giordano stated, “Nobody really knows the true mechanism behind this,” and the fundamental reasons why we yawn in the first place remain a subject of ongoing scientific inquiry.
Therefore, while we have a good grasp of the likely physical processes connecting yawning and tearing, the complete picture, down to the finest biological details, is still being researched. The next time you feel your eyes water mid-yawn, you can appreciate the complex interplay of facial muscles, tear glands, and drainage ducts working together – even if the ultimate “why” behind yawning itself remains a bit of a mystery.
