Concealers
Many people think that concealers are the same as foundations and, to some degree, that's true. In a way, you can look at concealers like concentrated foundations but the fact of the matter is, concealers have a very specific role to play and they have to perform in concert with foundations over which they are applied. And that means matching colors. In no event should you ever consider going more than one shade lighter or darker that you skin tone or foundation tone, especially when you're trying to hind large problem areas like under the eye circles. Studio Direct has a great selection of concealers with just the right colors I need for the camera.

That being said, concealers work well to hide circles under the eyes. Like all concealers, us it sparingly as it tends to "cake-up" and choose a pink- or peach-based concealer. Yellow-bases tend to combine with the dark colors to heighten the effect. For the areas of the face where light generally hit is, a yellow-based concealer is typically used. And, if you have fair skin, look for a concealer with subtle pink tones a shade darker than your skin. If you have dark skin, go for a copper-toned concealer a shade or two lighter than your skin.

The biggest issue with concealers after correct color selection is application. Where ever you use concealer, use as little as possible and then spread it out with your fingers or a concealer brush. If it's under the eyes, start at the upper, inner corner of your eye and blend down and under. Blend until product is completely absorbed. If it's for scars or birthmarks, 1) use concealer only use if the wound is healed to a scar and 2) if the birthmark or scar is extremely dark, use white first to lighten the area and then the concealer color closest to your skin tone over the white. In both cases, use a professional sponge to apply. Finally, on Rosacea or other problem areas, apply with a sponge and only to the areas needing coverage.