Parents often notice that when their baby starts rubbing their eyes, it’s a clear signal that nap time is near. But have you ever wondered why babies rub their eyes when they feel sleepy? What causes this behavior, and what role does it play?
Dr. Rebecca Dudovitz, an associate professor of general pediatrics at the UCLA David Geffen School of Medicine, shared with Live Science, “Unfortunately, we can’t ask a baby exactly why they’re rubbing their eyes.” She adds, “However, based on what we understand from human behavior, it’s common for people to rub their eyes when they’re tired. This could be due to a sense of discomfort that arises after the eye muscles have been active for a while and need to rest.”
Just like how your shoulders might crave a massage after a long day of sitting at a desk, the muscles that support your eyes’ focus also benefit from a gentle rub. Babies, who spend a considerable amount of time observing their surroundings, often experience tired eyes.
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Moreover, staring for extended periods can lead to dry eyes. Given that babies only blink a few times each minute, it’s not surprising that their eyes can become dry.
“Tears are more than just salt water. They consist of mucus on the surface, salt water in the middle, and a layer of oil from the eyelid’s meibomian glands to prevent evaporation,” explains Dr. Robert W. Arnold, an ophthalmologist at Alaska Children’s Eye & Strabismus, in an email to Live Science. “For healthy eyes, this tri-layer of tears needs to be continuously renewed and spread evenly across the eye’s surface through blinking.”
When we engage in intense visual concentration, we tend not to blink enough. This lack of blinking can disrupt the tear film, leading to dry spots on the cornea’s surface. In such cases, rubbing the eyes might serve as a reminder to blink more often.
“This is somewhat akin to how our breathing works. Normally, our breathing is automatic and sufficient. But when we’re distracted or tired, we might not breathe as often or as deeply as we should,” Arnold notes. “Therefore, we sigh. For children, rubbing their eyes could be similar to sighing, but for the health of their eyes.”
However, rubbing your eyes too much isn’t good for you. Excessive eye rubbing can cause vision problems.
One reason rubbing your eyes feels good when you’re tired is that it can lower blood pressure by stimulating the trigeminal and vagus nerves. These nerves run from the brain to the eyes and throughout the body, respectively. For some, this can lead to a significant reduction in heart rate, a phenomenon known as the oculocardiac reflex.
Yet, Arnold questions this explanation, saying, “There’s no clear reason why a slower heart rate would make a child feel better.”
In fact, the oculocardiac reflex can lead to dangerous outcomes, including bradycardia—a heart rate below 60 beats per minute—and even cardiac arrest.
Arnold concludes, “We don’t believe that intentionally triggering the oculocardiac reflex is a reason for children to rub their eyes, but it could be a consequence of excessive eye rubbing.”
Most likely, the reason babies rub their eyes is the same as for adults: their eyes are tired and dry, signaling it’s time for a rest.