Dark circles give the skin around your eyes, especially your under-eyes, a deeper or hyperpigmented tone. The area may take on a blackish, purplish, or brownish hue, depending on your skin color (via the Cleveland Clinic).
It’s possible to get dark under-eye circles if you rub your eyes excessively. As board-certified dermatologist Devika Icecreamwala explained to Huffpost, rubbing the sensitive skin around the eyes irritates and traumatizes it. The skin responds by getting thicker and darker. You may also break blood vessels under the skin if you rub it. Due to the thinness of the skin around the eye, damage to the blood vessels underneath it can become noticeable.
Apart from eye rubbing, there are a couple of other reasons why dark circles appear, such as stress, sun exposure, alcohol use, dehydration, or not getting enough sleep. They may also be caused by skin conditions like contact dermatitis or eczema. Dark circles appear more often if you have certain genes or due to aging. Generally, dark circles are not a cause for concern as they pass with time, though they do tend to make people look tired and older.