What causes dark circles?
A black marker pen.
No.
There are a number of reasons which cause dark circles.
Some of them are stress and lack of sleep.
Under these conditions, our body produces a hormone called cortisol.
Over time, cortisol constricts some blood vessels.
Dilates the others like the vessels around or under our eyes.
As a result, these blood vessels become bigger.
Now, when sunlight or any white light falls around our eyes.
Various colors which make up white light interact with the skin.
Blood vessels in such a way that they mostly reflect bluish light.
Now, as the skin around our eyes is thinner as compared to other parts of the body.
The big blood vessels that reflect bluish light are prominent.
This makes the area around or under our eyes appear darker, thus causing dark circles.