Q: What’s the best serum or ingredient to get rid of the dark circles under my eyes? A: A lot depends on the cause of your undereye circles, which can range from lack of sleep to genetics to dehydration. The good news is there are components that do help reduce undereye circles. Vitamin C is a trustworthy player in this respect, helping to brighten undereye darkness. Niacinamide provides a similar skin-brightening effect, and both are also terrific in many other aspects of skin health.