Vitamin C serum: what does it do?

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What is Vitamin C?

We know we should be eating plenty of vitamin C, but what’s the deal with vitamin C serum?

Free radicals are highly reactive molecules with unpaired electrons that are known to damage various cellular structural membranes, lipids, proteins, and DNA. It is one of the widely accepted mechanisms that lead to skin ageing.

The body can be exposed to free radicals from environmental exposures (as well as intrinsic exposures), such as cigarette smoke, air pollution, and ultraviolet radiation from the sun. Consequently, the body employs antioxidants which aim to protect cells from the damaging effects of free radicals.

Vitamin C reacts rapidly with free radicals; it is widely understood that vitamin C’s antioxidant properties are partly responsible for its biological activity.

Vitamin C is the most prevalent antioxidant already present in our skin. Vitamin C is also required for collagen production and has use in the reduction of fine lines. Thus, topical application of vitamin C has been shown to have many positive effects on the skin, ranging from collagen production to protection from environmental stressors.

So, why not simply ingest enough vitamin C in our diets or take supplements for these effects? Why do we need to apply it topically to reap the rewards?

As humans, we are unable to synthesise our own vitamin C and we typically get this vitamin from our diet instead. However, factors such as absorption, metabolism, and distribution, limit the amount of vitamin C that can eventually be delivered to the skin. Additionally, when this vitamin neutralises oxidative stress in the skin, it is used up. This is where topical application can be beneficial.

What should I look for on a product label?

Vitamin C in skincare can be found in both active and inactive forms. It is important we choose wisely if we want to see the beneficial effects that vitamin C has to offer. Vitamin C’s most active and well-studied form is known as ‘L-ascorbic acid’ and is present as ascorbate, a water-soluble molecule, in most biologic settings. So make sure to look for ‘L-ascorbic acid’ or ‘ascorbic acid’ on product labels (with or without the ‘L’ – they are the same compound, just the former is more descriptive).

L-ascorbic acid is more desirable in skincare products over derivatives (e.g. ascorbyl-6-palmitate, magnesium ascorbyl phosphate, disodium isostearyl 2-0 L-ascorbyl phosphate, ascorbic acid sulphate, tetraisopalmitoyl ascorbic acid) since it is the most effective and well-researched.

For vitamin C to be absorbed into the skin, the skincare product must be formulated at a pH of 3.5 or lower. Usually though, this isn’t something you need to worry about if you are purchasing a product from a reputable brand.

Vitamin C for Hyperpigmentation

Hyperpigmentation – a darkening of the skin that occurs due to an excess of melanin, for example, in the case of age spots, freckles, melasma, and post-inflammatory hyperpigmentation. Cosmeceuticals are commonly used to target hyperpigmentation; hydroquinone being a common example in the treatment of hyperpigmented skin conditions. However, hydroquinone has recently come under fire due to chronic adverse side effects such as discolouration of the skin, cataract, pigmented colloid milia, loss of elasticity of the skin, impaired wound healing as well as safety concerns.

Studies have show that vitamin C acts as a reducing agent at various oxidative steps of melanin formation, hence inhibiting melanogenesis. Thus, vitamin C is widely used in dermatology for depigmentation of hyperpigmented spots on the skin.

Another study compared the use of 5% ascorbic acid and 4% hydroquinone in female patients with melasma and found that there was a 62.5% and 93% improvement in appearance, respectively. Side effects were present in 68.7% of people with hydroquinone use, versus 6.2% with ascorbic acid. Despite hydroquinone being the better performer, vitamin C may have a role to play in the treatment of melasma, since it is mostly devoid of any side effects.

Vitamin C for collagen production/anti-ageing effects

With age comes reduced fibroblast activity, leading to fine lines and wrinkles in the skin due to loss of collagen and elastin. Fibroblasts have a dependence on vitamin C for the synthesis of collagen and the regulation of the collagen/elastin balance in the dermis.

The topical application of vitamin C has been shown to elicit anti-ageing effects by increasing collagen synthesis in the skin, resulting in an increase of the structural integrity of our skin as well as slowing down the loss of structural integrity due to decreased degradation of collagen.

Vitamin C for Redness

Vitamin C is known to improve skin erythema (redness) due to its ability to strengthen blood vessel walls since collagen is a major component of these walls.

For example, studies have showed that 5% vitamin C caused a significant erythema reduction in capillary skin and photoageing skin. The research was conducted on a group of 30 women. Erythema decreased by: 9% after 2 weeks; 16% after 4 weeks and 21% after 6 weeks.

Another study showed that application of 10% topical vitamin C was able to reduce UVB-induced erythema by 52%.

Vitamin C for protection against environmental stressors/photoprotection

Vitamin C can be useful in providing protection from ultraviolet (UV) radiation-induced oxidative stress. Such oxidative stress may result in acute (e.g. sunburn) and chronic photodamage (e.g. skin cancer and photoageing). Topically applied vitamin C has been shown to induce significant photoprotective effects at concentrations of at least 10% in humans. This same photoprotective effect has not been demonstrated by oral administration (even at high doses) in humans.

P.S. This is not an excuse to skip sunscreen!

Vitamin C DOs and DON’Ts


  1. Since Ascorbic acid is a weak sugar acid it is wise to avoid the use of alpha-hydroxy and beta-hydroxy acids at the same time to avert irritation (and avoid a disruption in the pH, unless the vit. C is formulated with other acids then the pH should be fine, but in this case, stop usage if you find irritation occurring).
  2. Avoid the use of benzoyl peroxide since this is a powerful oxidant – or say hello to potentially deactivated vitamin C.
  3. Furthermore, if you use retinol (or other retinoid), to avoid irritation it is best to apply vitamin C in the morning and retinol in the evening. In addition, it’s best to avoid usage at the same time to avoid disrupting the ideal pH level used in each specific formulation (or having any unwanted interactions occur). Retinol products are typically formulated at higher pH’s.


  1. Use in combination with vitamin E. Vitamin C and E act synergistically in many biological systems – these vitamins help to protect each other and increase overall effectiveness. Ferulic acid (plant antioxidant) is another one to look out for, since it results in improved chemical stability of vitamins C and E.
  2. Use daily for maximum effect (or less frequently if your skin finds it particularly irritating).
  3. Certainly, application in the morning, on a clean face is the preferred time to apply for most people. This way one can reap its photoprotective effects to a greater extent. If, however, you are just looking to tend to some hyperpigmentation, then consistency is key, whether that’s through application in the morning or night. Although, if you are a retinol user then it’s best to apply your vitamin C in the morning and retinol at night.
  4. Check that the percentage of vitamin C is between 10-20% (for the greatest effect). Remember that 10% of a vitamin C derivative may not actually supply 10% of pure vitamin C. So check the label to make sure. P.S. serums tend to typically offer higher concentrations of vitamin C (skin penetration is also typically better with serums).
  5. Look out for ‘L-ascorbic acid’ or ‘ascorbic acid’ on product labels since this is the most effective and well-studied form of vitamin C.
  6. Lastly, to make sure the vitamin doesn’t degrade, look for products in airtight, opaque packaging to avoid exposure to UV rays, or the air.

Top picks

Note: all recommendations below contain pure vitamin C (ascorbic acid) rather than its derivatives.

Neutrogena Rapid Tone Repair 20% Vitamin C Brightening Serum Capsules

First up, an affordable favourite; these come in capsule form to protect vitamin C from the environment and avoid its degradation. Although less cost effective per use, the product itself is generally more effective than non-capsule forms. This product also boasts 20% vitamin C.

Paula’s Choice BOOST C15 Super Booster

Paula’s Choice C15 super booster offers 15% vitamin C along with vitamin E and ferulic acid. The perfect blend!

La Roche-Posay Pure Vitamin C Face Serum

For those with less sensitive skin or acne prone skin, then this serum might be a good option for you – along with 10% vitamin C, this serum also contains salicylic acid. Although a BHA, since salicylic acid has been formulated into this product pH needn’t be a worry, but those with sensitive skin should steer clear. This serum also contains hyaluronic acid – great for parched skin.

BeautyStat Universal Universal C Eye Perfector

An eye-specific vitamin C product – since it is meant for the delicate eye area this product is formulated with 5% vitamin C, along with hyaluronic acid and green tea extract.

SkinCeuticals C E Ferulic

The winner of many awards, this serum combines vitamins C (15%) + E with ferulic acid to maximize performance. This patented serum may be expensive, but is clinically proven to reduce combined oxidative damage from free radicals generated by UV, Ozone, and Diesel Exhaust by up to 41%

Key takeaways

Look out for ‘L-ascorbic acid’ or ‘ascorbic acid’ on product labels since this is the most effective and well-studied form of vitamin C.

Look for between 10 and 20% ascorbic acid for optimum effect.


Packer, J. E., Slater, T., & Willson, R. L. (1979). Direct observation of a free radical interaction between vitamin E and vitamin C. Nature278(5706), 737-738.

Lin, J. Y., Selim, M. A., Shea, C. R., Grichnik, J. M., Omar, M. M., Monteiro-Riviere, N. A., & Pinnell, S. R. (2003). UV photoprotection by combination topical antioxidants vitamin C and vitamin E. Journal of the American Academy of Dermatology48(6), 866-874.

Lin, F. H., Lin, J. Y., Gupta, R. D., Tournas, J. A., Burch, J. A., Selim, M. A., Monteiro-Riviere, N. A., Grichnik, J. M., Zielinski, J., & Pinnell, S. R. (2005). Ferulic acid stabilizes a solution of vitamins C and E and doubles its photoprotection of skin. The Journal of investigative dermatology125(4), 826–832.

Eberlein‐König, B., & Ring, J. (2005). Relevance of vitamins C and E in cutaneous photoprotection. Journal of cosmetic dermatology4(1), 4-9.

Sarkar, R., Arora, P., & Garg, K. V. (2013). Cosmeceuticals for Hyperpigmentation: What is Available?. Journal of cutaneous and aesthetic surgery6(1), 4–11.

Espinal‐Perez, L. E., Moncada, B., & Castanedo‐Cazares, J. P. (2004). A double‐blind randomized trial of 5% ascorbic acid vs. 4% hydroquinone in melasma. International journal of dermatology43(8), 604-607.

Al-Niaimi, F., & Chiang, N. (2017). Topical Vitamin C and the Skin: Mechanisms of Action and Clinical Applications. The Journal of clinical and aesthetic dermatology10(7), 14–17.

Darr, D., Combs, S., Dunston, S., Manning, T., & Pinnell, S. (1992). Topical vitamin C protects porcine skin from ultraviolet radiation-induced damage. The British journal of dermatology127(3), 247–253.

Jaros A, Zasada M, Budzisz E, Dębowska R, Gębczyńska-Rzepka M, Rotsztejn H. Evaluation of selected skin parameters following the application of 5% vitamin C concentrate. J Cosmet Dermatol. 2019;18:236-241.