In order to treat your circles properly, you first need to know what's causing them. According to Waldorf, "Dark circles may be due to pigmentation, blood vessels or an effect of the shadow of the tear through [the muscles and ligaments near the eyes on either side of the nose]."

If you pull the skin under your eyes taught and the circles seem to go away, your issue is likely the effect of a shadow. If not, your circles are likely blood vessels. As you age, your skin gets thinner, making red and blue vessels show through. If your circles don't look red and bluish though, pigmentation could be the cause of your circles -- this is most common among Asians and African Americans.

Next: Dark circle treatments

If your dark circles are caused by pigmentation, you can treat the area with topical retinoids, hydroquinone or laser treatments, Waldorf says. Both retinoids and hydroquinone can be prescribed by your dermatologist or you can buy slightly less potent versions over the counter (try Avene Retrinal H.A.F Gel, $40, which contains retinaldehyde, and pH Advantage Pigmentation Fader, $55, which contains hydroquinone). If you want a quicker fix (or if topical products alone don't do the trick), laser is the way to go. Waldorf recommends the Fraxel Restore laser. Know that you'll likely have to treat your entire face for best results though, and that treatments average $1,000 to $2,000 each and you'll likely need one or two of them.

Next: How to treat dark circles caused by blood vessels

If your dark circles are caused by visible blood vessels, look for "anything that vasoconstricts," to help reduce the darkness, Waldorf says. Caffeine is the most common ingredient found in skin care products that fits that bill (try Replenix CF, $56 or Garnier Nutritioniste Skin Renew Anti-Puff Eye Roller, $12.99). Your other option (especially if products alone don't solve your issue) is to get laser treatments with a laser like the VBeam, which Waldorf says will significantly improve the appearance of the vessels. VBeam can be used just on the eye area (as opposed to having to treat your whole face). It costs $200 to $400 per treatment and you'll likely need two to four treatments.

Next: How to treat dark circles caused by shadows

If shadows are causing your dark circles, you unfortunately have one basic treatment option -- you can fill the area between the bridge of your nose and the inner corners of your eyes (the tear through) with fillers like Juvederm or Restylane, Waldorf says. Beyond that, there isn't much you can do with skin care products to lessen the shadowy effect. However, all dark circles look worse when your skin is dry, so "improving the texture of your skin with proper moisturization is important also," Waldorf says.

Next: Conceal dark circles like a pro

Until you get rid of your circles for good, or if you'd rather just hide them in lieu of treating them, use Turnbow's tricks to conceal all types of dark circles:
Step 1: Massage on an eye cream in a circular motion with a cool fingertip to improve circulation.
Step 2: Use a firm tapered brush (try Clinique Concealer Brush, $19.50) to apply creamy concealer (Turnbow's fave: La Mer The Radiant Concealer SPF 25, $65) that's half a shade lighter than your skin and slightly peach-y in tone over the dark areas. Avoid shades that are too light or cool in tone or the area will look ashy. Also, don't forget to cover the darkness on the inner corners of your eyes.
Step 3: Tap a fingertip over the concealer to further blend it into your skin.
Step 4: If your eyes appear very sunken in and shadowy, apply a luminizing cream or powder (try Dior Skinflash, $34) over the concealer to make the area pop and appear brighter.

Next: Learn how to treat puffy eyes