resurrecting this old thread.

found this product and just thought i would share their theories on what causes the dark eyes.

www.dermalexmd.com/dark-circles.html

found the thread here on a search for the topic.

here's their take bearing in mind they are also selling a product...

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What are dark circles under the eyes?

Dark circles are formed by the same biological process that causes bruises to turn dark blue/purple.

When something strikes your skin, small blood vessels are ruptured. Blood leaks into the surrounding tissue. Your body has a system in place to deal with this, and an enzymatic reaction starts breaking down the leaked blood so your body can metabolize it. A side-effect of this process is that the waste products are the familiar dark purple-blue of a bruise.

The delicate skin around the eyes (also called peri-orbital skin) is very thin. This skin is nourished by a web of capillaries. From time to time, these capillaries leak small amounts of blood. As the body's enzymatic reaction goes to work, the same purple-blue coloration is produced beneath the skin, leading to dark circles. (It's more visible under the eyes because the skin there is so delicate and thin, and in many people, more translucent.)

Dermalex-MD works by accelerating the enzymatic process that gets rid of the purplish coloration. Other ingredients strengthen capillaries, effectively helping to prevent dark circles before they even start.

What causes dark under eye circles?

Most people think dark under-eye circles are caused by staying up too late. This isn't the case: in fact, lack of sleep makes the skin around the eyes paler, allowing the purplish color to be more visible. Anything that makes your face paler (illness, menstruation, etc.) make dark circles look darker.

Spending time in the sun also makes dark circles look darker. Allergies can cause dark circles to appear (sometimes simply due to rubbing the eyes!).

The primary "cause" of dark circles is hereditary. You inherit from your parents the genes that determine the strength of the capillaries in your skin -- determining exactly how "leaky" these capillaries are. Furthermore, heredity can determine the thickness and opacity of the skin around your eyes, which can make dark circles look even worse.