Long dark circles are usually caused by vascular factors, pigmentation, and structural factors. 1. Vascular factors: the skin tissue around the eyes is thin and the capillaries are distributed more, due to lack of sleep and other reasons leading to continuous contraction of the capillaries around the eyes, the blood in the blood vessels is stagnant under the eyes, which will reveal a dark black shadow. 2. Pigmentation: Ultraviolet radiation, repeated inflammation can lead to skin pigmentation around the eyes resulting in dark circles. 3. Structural factors: Individuals with puffy bags under the eyes, tear troughs exist under the eyes to form a shadow, leading to the visual appearance of dark circles under the eyes. Long dark circles under the eyes may also be caused by other diseases, such as has appeared to be other aspects of physical discomfort, it is recommended to go to the regular hospital as soon as possible to treat the symptoms.