You can use a lighter shade of foundation as a concealer if you only need to brighten the area under your eyes. However, foundations have a lighter formula than concealer. So, if you’re looking for full-coverage this may not work. Foundation and concealer have almost the same consistency. The main difference between the two is the coverage. Yes, some foundations offer full coverage. But that does not beat the concealing power of concealers. Foundations are meant to provide an overall smooth finish that evens out the skin tone. Concealers, on the other hand, has a slightly thicker formula. This helps hides the dark undereye area, blemishes, and dark spots. You’re most likely to use less concealer than foundation.