Choosing a concealer might drive you insane! I'm always on the hunt for a great concealer. I actually like and use quite a few different ones (I alternate depending on the day). I use an eye primer, under eye primer, corrector and under eye concealer everyday. It's hard to find the right combination of everything. I know that sounds like a lot for everyday but you can definitely slim that down. Here are ones that I have tried.
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Under eye concealers should cover dark circles or brighten up the eye, so the consistency should be light not heavy or cakey.
Blemish concealers...you never know when you will need one. For some reason in my 20's I broker out with adult acne, I never had a day without wearing blemish concealer! I have gotten my skin under control the last few years (through many many skin care product trials...that's a whole other story) but I always keep a blemish concealer in my makeup bag.
I started using correctors a couple of years back. I didn't feel the need to use an undereye concealer until a couple years back which in turn started my endless journey for the perfect concealer. When I started trying concealers nothing I tried looked right. The concealer always seemed to do the opposite of what I was trying to achieve. Concealer always looked ashy on me no matter what shade tone I tried until I started using a corrector. If you have blue or purple circles you would want to use a pink-based corrector. If you have more brown or green toned circles you will want to use a peach-based corrector. It makes a world of difference! Right now there is a new trend of skin correcting. Personally I would use correctors sparingly only where needed.