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Benefits of Vitamin C

From boosting radiance to helping diminish the signs of aging to antioxidant protection, Vitamin C is a highly efficacious skincare ingredient with a wide range of benefits. With all of the myths and misinformation circulating about Vitamin C, learn the truth about the benefits of using a Vitamin C serum for your skin.


Vitamin C, or ascorbic acid, is a powerful antioxidant that promotes a healthy immune system, helps improve wound healing, maintains connective tissue, and aids in the absorption of iron. It also helps block some of the damage caused by free radicals which, over time, are largely responsible for the aging process.


Yes. Vitamin C is key to the production of collagen and elastin in the skin and is the primary replenisher of vitamin E, which protect cells against oxidative stress. Because of its antioxidant properties, Vitamin C may help improve the negative effects of UV radiation in the skin.


Just as Vitamin C is an essential part of your diet, it is also an important step in your skincare routine. The human body does not produce its own Vitamin C but relies on obtaining it through nutritional and topical applications, which help fight skin damaging free radicals that can lead to future signs of aging. Daily use of a balanced and stabilized Vitamin C facial serum will ensure that your skin soaks up all of the perks of this powerful ingredient. Vitamin C has been known to have an anti-aging effect on skin by helping to improve deep lines, wrinkles, uneven skin texture, and dullness.


Kiehl’s became pioneers in Vitamin C skincare when our chemists stabilized 10.5% Vitamin C in our potent Vitamin C serum. This customer-favorite formula is now formulated with 12.5% Vitamin C* and Hyaluronic Acid and penetrates skin’s deeper surface layers to help visibly reduce lines and wrinkles, minimize the appearance of pores, help firm skin and boost radiance. With 10.5% L-Ascorbic Acid and 2% Vitamin Cg, the antioxidant Vitamin C in our patented formula remains in skin for up to 6 days.

Learn more about this trusted ingredient and how to choose the best Vitamin C products to use in your daily skincare routine.

Fact: Not All Vitamin C Serums are Created Equal

There are actually several different forms of Vitamin C that are used in skincare formulas. While they have overlapping benefits, Pure Vitamin C (L-Ascorbic Acid) is absorbed into skin and starts working immediately upon contact while Vitamin Cg (Ascorbyl Glucoside) activates once absorbed into the upper layers of skin to boost Vitamin C activity over time. Kiehl’s Vitamin C serums and formulas effectively incorporate a form of topical Vitamin C that is carefully selected to maximize its targeted efficacy.

Fact: The More Vitamin C, the Better

While it may seem like a higher level of Vitamin C would be better, these formulas can actually cause sensitivity or be less effective if they are not stabilized properly. When products have concentrations of L-Ascorbic Acid that are too high, skin can even experience irritation. Kiehl’s selects the best forms of stabilized Vitamin C at concentrations that are both efficacious and gentle. Our products are then dermatologist-tested for safety, demonstrating the suitability of our formulas for all skin types, including sensitive skin.

Fiction: DIY Vitamin C Serums are as Effective as Other Formulas

L-Ascorbic Acid is an unstable ingredient, meaning it can be oxidized when it is exposed to light, air, or heat and become less effective. This powerful form of Vitamin C can be challenging to stabilize within serums and needs to be formulated at a specific pH level to ensure that it effectively delivers benefits to skin. Kiehl's became pioneers in Vitamin C skincare when we first stabilized L-Ascorbic Acid in our water-free formula more than 15 years ago.

“When exposed to water, Pure Vitamin C can degrade, causing it to lose its effectiveness. A water-free formula (like Powerful-Strength Line-Reducing Concentrate) helps keep high concentrations of Pure Vitamin C stable and effective.” – Dr. Megan O’Brien, Kiehl’s Consulting Dermatologist

Fiction: Vitamin C Serums Cause Skin Sensitivity to the Sun

In actuality, topical Vitamin C has been demonstrated to be a second line of defense against harmful UVA rays while also helping to bolster skin’s antioxidant defenses. We recommend applying a Vitamin C serum in the morning before adding a daily sunscreen.

Fact: Vitamin C Products Benefit All Skin Types

Vitamin C facial benefits extend to all skin types, including sensitive and dry skin. In addition to helping visibly fade discolorations or diminish fine lines and wrinkles, using a Vitamin C serum can also provide antioxidant protection to help defend from skin-damaging free radicals.

Fiction: Vitamin C Serums are Not Suitable for Sensitive Skin

At Kiehl's, our Vitamin C serums are carefully formulated to be gentle enough for sensitive skin and are tested on panels of 50% sensitive skin individuals. When first beginning to use a Vitamin C serum, start with a once-daily application, and gradually build to twice a day. Always consult with your dermatologist when incorporating new skincare products into your routine.

Fact: Store Your Vitamin C Serum in a Cool, Dry Place

Store L-Ascorbic Acid serums in a place other than your bathroom cabinet as they are best kept in an area without humidity. Additionally, L-Ascorbic Acid serums in dark-colored or amber bottles can help protect the formula from light.

Fact: Apply Vitamin C Serums Before Your Moisturizer

After you cleanse and tone your skin, apply a thin layer of your serum. Smooth it on morning and night before your moisturizer to help lock in the skin benefits of your Vitamin C serum.

Fiction: Vitamin C Serums are Only for the Daytime

While Vitamin C help defends skin during the day, it is also an effective ingredient to use in your nighttime skincare routine. In our formula, the antioxidant Vitamin C remains in skin for up to 6 days! For best results, use your Vitamin C serum twice a day, morning and night.

Fact: Vitamin C Serums are Not Just for Anti-Aging

Vitamin C levels deplete in skin over time, so using skincare products with Vitamin C is important as you grow older. However, these formulas are still effective to use before you start to see fine lines and wrinkles. These formulas help boost radiance and provide antioxidant protection to help defend skin from early signs of aging.

Types of Vitamin C in Skincare

Pure Vitamin CL-Ascorbic Acid, or Pure Vitamin C, is a powerful skincare ingredient that easily absorbs into skin and begins working immediately. A dermatologist-recommended ingredient, L-Ascorbic Acid is frequently used in anti-aging skincare products to improve radiance and skin texture while helping to diminish the appearance of fine lines, wrinkles and crow’s feet. Kiehl’s Vitamin C serum is formulated with 10.5% Pure Vitamin C.

Vitamin CgVitamin Cg, or Ascorbyl Glucoside, is a potent derivative of Vitamin C that provides antioxidant protection and helps to minimize the visible signs of aging. Kiehl’s Powerful-Strength Line-Reducing Concentrate is formulated with 2% Vitamin Cg to help enhance the efficacy of Vitamin C benefits over time. It is also found in our customer-favorite men’s moisturizer.

Activated CActivated C is a next-generation Vitamin C derivative that is highly efficacious. Within our formulas, this powerful form of Vitamin C penetrates skin’s surface and is known to help fade dark spots and skin discolorations. Activated C is a key ingredient in Kiehl’s dark spot corrector and brightening face mask.