In the battle against hyperpigmentation and dark spots, vitamin C is pretty much the best over-the-counter product in your skin-care arsenal. The potent antioxidant eliminates free-radical damage from the sun, pollution, and various other environmental stressors, and helps your skin regenerate and repair damaged cells. In the same way it’s wise to incorporate vitamin C–rich foods like oranges, kale, and tomatoes into your diet to keep your body healthy, a topical treatment will only improve your skin’s ability to heal itself.

However, not all vitamin C products are created equal. The ingredient is fairly unstable and can quickly grow ineffective after a few months on your shelf. You can spot a formula that has gone bad once the serum oxidizes (meaning it has come into contact with oxygen for too long and has undergone a chemical change) and turns yellowish brown. Luckily, brands are coming up with new methods of formulation to ensure that your favorite products stay potent longer. That means you can continue using them until the bottle runs out without sacrificing efficacy. More beauty bang for your buck, so to speak. These five new serums are just a few of our current favorites. Check them out below.