If you’ve over a certain age – or if you have kids – there’s a good chance you’ve looked in the mirror and been shocked at the dark bags under your eyes.

We know they show up when we’re lacking sleep and unable to catch up, but why?

The skin around our eyes is thinner than the other skin on our body and face, which is why it’s more prone to sagging, lines, and wrinkles.

As we age and the skin thins further, it’s easier to see blood vessels, pigmentation, and sunken spots.

And when we’re overly tired or stressed, our body produces cortisol. It’s a steroid hormone that’s secreted by our endocrine glands, and is released (among other times) when our body is trying to stay awake and alert.

High cortisol can increase the appearance of eye bags because it pumps up our blood volume with extra proteins and plasma. The vessels become engorged, and for a pale person, that means dark circles that will make eye bags more pronounced.

Some people are unfortunate enough to sport dark circle all the time, whether they are well-rested or not, and genetics definitely come into play.

In addition to genetics and fatigue, things like too much alcohol, salt, or nicotine can also dilate blood vessels like cortisol levels and make those bags more visible.

Some research also suggests that frequent use of/removal of cosmetics can cause wear and tear that mimics aging as well.

Losing weight/fat can have similar effects as well.

The truth is that almost everyone has eye bags at one time or another, and while seeing those dark smudges might be surprising, they’re a natural feature.

Getting enough sleep is important for everyone’s health, so if you don’t like yours, start there.

The benefits will far outstrip a brighter face in the morning.

If you found that story interesting, learn more about why people often wake up around 3 AM and keep doing it for life.