Sleeping for too long, or a lack of sleep, may cause your skin to become more dull, turning the blood vessels pale and dark beneath your skin.
Dry eyes or allergic reactions may cause dark circles. When you have an allergic reaction, body releases histamines to fight off the invader causing itchy, red, and puffy eye and ultimately leading to post-inflammatory pigmentation.
Dehydration can contribute to the appearance of dark circles under the eyes. When you're not well-hydrated, the skin under your eyes loses plumpness, making the underlying blood vessels more visible.
According to few studies genetics may contribute to the development of POH (Periorbital Hyperpigmentation). The study found a strong association between POH and family history, due to which it can be inherited early in childhood.
Anemia is when your levels of red blood cells are lower than normal. If you have anemia, you may notice that your skin is paler than usual.