The darkness in the lower lids can come from the vascularity with dark blood in the veins showing through. Also, if there are tear troughs then shadows across the hollows will look dark.
What Causes Darkening of Eyelids and Skin Around Eyes?
Doctor Answers 3
Dark circles around eyes.
There are two different kinds of darkening. The traditional darkening is due to the thin skin and visibility of the underlying muscle. Just like veins can look blue under your skin. Your muscle under your eye skin can look blue.
Alternatively, the skin can have a brown appearance that is related to pregnancy or hormones and is called chloasma or commonly knownw as the "mask of pregnancy."
Vascular and Pigmentation
The color is an interplay between vasculature, including any blood which may have leaked out of the blood vessels, and pigmentation. Blood in this area breaks down into its own hemosiderin pigment. Then there is the natural pigmentation of this area, pigmentation which may be increased by sun exposure.
These answers are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.