Vitamin C Serum: All That You Need To Know

A great number of anti-aging preparations containing vitamin C and its derivatives have been marketed over the last few years with specious claims for their protective and rejuvenating skin effects. In today’s article we’ll talk about vitamin C serum and all that you need to know before using it.

Vitamin C Serums

We’ve all been scouring the internet daily to find “the” product that actually works and at the same time, won’t make your wallet cry. But before we start with vitamin C preparations, let me brief you in with what we know at this time. If you are following my blog regularly, you might be knowing already that I believe: good sun protection is the best approach, and this is irrespective of what products you’re using during the day and night. However, this, together with a good vitamin C serum can really step up your skin protection game.

Vitamin C Serum

Vitamin C: its role in skincare

Through out the course of life, our skin is exposed to a number of challenges that can affect its structure, function and appearance. These challenges include, but are not limited to: environmental and chemical elements that accelerate wrinkling, normal skin aging, as well as direct and indirect injuries to the skin, such as wounding and burning.

Overall, vitamin C is involved in the formation of the skin barrier and collagen synthesis. It also plays a preventative role against skin oxidation, in anti-aging of wrinkles, and in cell signal pathways of cell growth and differentiation.

Vitamin C Serum Face
Image credit: Unsplash

What do we know about vitamin C?

  • Vitamin C is available in several active forms, but among all forms, L-ascorbic acid (LAA) is the most biologically active form and thus useful in medical practice.
  • In nature, vitamin C is found in equal parts as LAA and D-ascorbic acid.
  • It is unstable and, on exposure to light, gets oxidized to Dehydro Ascorbic Acid (DHAA), which imparts a yellow colour.
  • L-ascorbic acid is a hydrophilic and unstable molecule, hence the poor penetration into the skin because of the hydrophobic character of the stratum corneum.
  • L-ascorbic acid is also a charged molecule, and the ionic charge further limits its penetration.
  • However, by maintaining a pH of less than 3.5, the ionic charge is removed and the molecule is transported well across the stratum corneum.
  • Two other common topical formulations of vitamin C include ascorbyl-6-palmitate and magnesium ascorbyl phosphate (MAP). Unlike L-ascorbic acid, which is hydrophilic and unstable, both ascorbyl-6-palmitate and MAP are lipophilic, esterified forms of vitamin C, and are stable at neutral pH.
  • MAP has a hydrating effect on the skin and decreases transepidermal water loss. It is also a free radical scavenger that is photoprotective and increases collagen production under laboratory test conditions.

Most reputable products contain vitamin C between 10 – 20%. It is known that increasing the concentration above 20% offers no greater advantage, conversely, may cause skin irritation and reactions.

Stability, absorption, and cutaneous effects of vitamin C together with some commercially available derivatives (reference cited below)

Watch out for potency and stability

  • The stability of vitamin C in topical solutions is a major source of concern, as exposures to air, heat, and/or light may slowly degrade the active ingredient and render it less effective.
  • Ascorbic acid —while it is considered to be highly effective for topical administration, it is also the least stable of all derivatives.
  • Other stable synthetic derivatives, such as ascorbate phosphate have limited permeability.
  • However, the stability of topical vitamin C solutions can be increased with the addition of other antioxidant compounds such as Vitamin E, Ferulic or zinc.

Even though the use of topical ascorbic acid is highly effective, it is also the least stable form in solution.

Remember, it’s your morning vitamin

Because vitamin C protects your skin from free radical damage, we recommend using your serum as part of your morning routine. You can use your serum once daily or even every other day, and it should go without saying that topping it up with a broad spectrum sunscreen is essential.

Why is pH so important?

Skinceuticals C E Ferulic Saharreviews

The skin has a pH of around 5 and ascorbic acid (vitamin C) is a weak acid. In terms of chemistry, when the pH is less than the pKa of ascorbic acid (4.25), the molecule is actively protonated, i.e., it becomes more lipophilic (neutrally charged) and it is readily absorbed into the skin.

Vitamin C formulations with a pH below 4.0 will penetrate the skin more readily.

Skinceuticals Phloretin CF
Vitamin C is an essential part of my routines

But, aren’t most vitamin C serums expensive?

While this might come as a surprise for some of you, once L-ascorbic acid is applied to the skin, it is immediately absorbed. Not only that, but it cannot be washed off, and will remain in the skin for up to 72 hours. This is why some dermatologists even recommend using vitamin C serum each alternate night, with your retinoids.

Here’s the good news: once absorbed into the skin, vitamin C is present and active for up to 72 hours! So it is safe to say that you can even use your favourite vitamin C every other night.

We all know that good, pure and effective vitamin C formulations are very expensive. This for me, is an important factor to consider; using it every other night will ensure your favourite serum not only lasts longer but your skin reaps the full benefit of the vitamin.

How to store it?

Vitamin C serums typically have a shelf life of four months after opening. Another point to note is that fresh active vitamin C serum should be clear and should have a yellowish color. Over time, you will notice the serum turns dark brown/orange due to oxidation of vitamin C to dehydroascorbic acid.

Therefore, it is advisable to use the bottle within 3 months after opening and to throw it out if you notice changes in the texture and appearance of the serum, as this might induce skin irritation. Always make sure you are storing your vitamin C serum in a cool, dry place such as a cupboard and that you close the bottle as quickly as you can after each use.

It is always best to conduct a patch test and consult your dermatologist before starting a new product.

Now that you know all about vitamin C, you can go ahead and read my reviews of some vitamin C serums. These include Skinceuticals CE Ferulic, DERMAdoctor Kakadu C 20%, Dermalogica Biolumin C and Shirley Conlon Organics Vitamin C Elixir.


Ponec, M., Weerheim, A., Kempenaar, J., Mulder, A., Gooris, G. S., Bouwstra, J., et al. (1997b). The formation of competent barrier lipids in reconstructed human epidermis requires the presence of vitamin C. J. Invest. Dermatol. 109, 348–355.
Stamford NP. Stability, transdermal penetration, and cutaneous effects ofascorbic acid and its derivatives. J Cosmet Dermatol 2012; 11:310-7
Vitamin C in Health and Disease. Anitra C. Carr and Jens Lykkesfeldt
Farris, P. K. (2005). Topical vitamin C: a useful agent for treating photoaging and other dermatologic conditions. Dermatologic surgery, 31(s1), 814-818.
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 Dermatology, 48(6), 866-874.

Sahar x


  1. 23rd June 2020 / 12:08 pm

    This is a fabulous informative post. Thank you Sahar xx

    • Sahar Reviews
      23rd June 2020 / 9:43 pm

      Thank you Sal, I’m glad you found it useful. 🙂

  2. Juli Prouse
    10th October 2022 / 1:57 am

    Thank you for the very informative article. Are there any significant updates to the table since your article was posted? I am particularly interested in the effect on collagen synthesis, as well as conversion to ascorbic acid of the various derivatives.

Leave a Reply

Your email address will not be published.

Please turn AdBlock off

error: Content is protected !!