Both Dr. Lolis and Mamina Turegano, MD, a dermatologist, internist, and dermatopathologist in Metairie, Louisiana, are big fans of this cult-classic serum because it contains a powerful and patented blend of vitamins C, E, and ferulic acid, which works hard to correct discoloration and target the signs of aging, like fine lines and wrinkles.

“Vitamin C helps boost collagen production, brightens the skin, and reduces the appearance of age spots,” says Dr. Lolis. “In this serum, there’s a concentrated dose of it that’s also paired with vitamin E, which further enhances the anti-aging benefits of the vitamin C,” she adds. The inclusion of ferulic acid enhances the antioxidant advantages by stabilizing vitamins C and E so they don’t degrade over time once you’ve opened the bottle, says Dr. Turegano. This serum is so effective at tackling discoloration, in fact, that it took the top spot in our tests of the best dark spot correctors.

Underwood admits it doesn’t have the best smell and the texture is a bit on the oily side, but says it’s hard to replicate this formula’s results when it comes to tackling discoloration. Many brands have tried, but this OG holds steady, he says. “I’ve been using it for years and have always been impressed by the results.” His pro tip for maximizing your investment? Only use a small dab—the formula is runny, so a little bit goes a very long way.