Today’s Wonder of the Day was inspired by Caden. Caden Wonders, “why do your eyes develop shadows when you're tierd?” Thanks for WONDERing with us, Caden!

"I love bedtime!"…said no child ever. Does that sound like you? Do you constantly think of excuses to stay up just a little bit later than you know you're supposed to?

If so, you're not alone. Bedtime is not the favorite time of day for most kids. It can be hard to shut down and prepare for sleep, especially if it's summer and it's not even dark outside yet.

Every once in a while, you probably get the chance to stay up late, such as when you have friends visit for a sleepover. Whether it's a movie or video game marathon, it can be fun to stay up until the wee hours before finally crashing and then sleeping in late.

When you wake up that next morning (or afternoon!), though, it can be a bit surprising when you look in the mirror. If you're like many people after an all-nighter, there might be tell-tale signs below your eyes. That's right. We're talking about dark circles or bags under your eyes.

Have you ever had dark circles or bags under your eyes? They're a common problem that many people deal with, and there are actually many different things that can cause them. The clinical term for this phenomenon is periorbital hyperpigmentation (POH).

If you run your fingertips over the skin just below your eyes, you can feel how thin it is. Since it's so thin, it's fairly transparent, allowing you to see through to the tissues and blood vessels underneath it.

Anything that causes increased blood flow to the area underneath the eyes will make the skin there appear darker. This is due to the red, blue, and purple pigments in blood, which can be more easily seen through the thin skin below the eyes when blood flow to that area increases.

Likewise, the skin beneath the eyes is also extra sensitive since it's so thin. Anything that irritates the skin below the eyes can cause it to thicken or swell, creating the "bags" we often see below our eyes.

So why does lack of sleep so often lead to dark circles and bags under the eyes? Not getting enough sleep often causes the blood vessels under the eyes to dilate, increasing blood flow and causing dark circles.

When you don't get enough sleep, the body also often produces cortisol to increase energy levels. This hormone can cause blood vessels to dilate. It can also cause water retention, which can make your eyes look puffy.

Lack of sleep isn't the only culprit, however. You might see dark circles or bags under your eyes as a result of other causes, such as allergies, dehydration, poor diet, stress, smoking, aging, sun exposure, and lack of exercise. Some people may also be prone to dark circles and bags under their eyes as a result of skin tone and/or genetics.

Is there any way to get rid of those dark circles and bags under your eyes? The obvious answer is to get more sleep. If you don't have time for a nap, though, you might try eye creams, makeup, or placing cool, damp tea bags under your eyes. The tannic acid in the tea leaves can help to reduce swelling and cause the blood vessels to shrink.

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