What you need to know about vitamin C

There is no doubt that vitamin C is good for the skin. It has been clinically proven to protect against photoaging (skin ageing due to sun exposure), reverse environmental pollution damage on the skin, and brighten complexion by inhibiting melanin overproduction. A perfect ingredient for a healthy, radiant skin.

But do we really know how to use vitamin C in a beauty routine to maximise its benefits? Read on to find out how to make the most of this wonderful ingredient.

Know your vitamin C

Vitamin C is the most abundant vitamin in human skin, yet our bodies can’t produce it. What is more, clinical trials show that food and oral supplements with vitamin C don't have much effect on the skin, and only vitamin C applied to the skin topically can deliver visible benefits.

There are many skin care products containing various forms of vitamin C, mainly L-ascorbic acid but also novelty, more stable and less skin-irritating forms of vitamin C such as Tetrahexyldecyl Ascorbate, Ascorbyl-6-Palmitate and a few other (difficult to pronounce) forms of vitamin C.

Which vitamin C is best for the skin?

To enjoy powerful antioxidant, antiaging and skin brightening benefits of vitamin C, it has to penetrate the epidermis (the outer layer of skin) and convert to L-ascorbic acid in the dermis (middle layer of the skin where restorative processes occur). It will then increase skin firmness, support collagen synthesis and fight free radicals and reduce sun damage. But are all forms of vitamin C equal? Let’s look at their pros and cons.

L-Ascorbic Acid

Water-soluble, very popular form of vitamin C. L-ascorbic acid is used in water containing products like serums, creams, toners etc.

PRO TIP: L-ascorbic acid is notorious for its instability. This means it oxidises in cosmetics very quickly, losing its efficacy sooner than you can use up the product. Don't buy serums with L-ascorbic acid larger than 15ml / 0.5oz.

  • Very effective;
  • Quickly visible results;
  • Commonly used in cosmetic products;
  • Inexpensive.
  • Extremely unstable;
  • Low skin penetration;
  • Requires pH 3.5 to be effective which can cause skin irritation, redness and sensitivity;
  • Cannot be paired with strong actives like as retinol;
  •  Advised to use only in the evening.

Oil-soluble vitamin C

Vitamin C esters like Ascorbyl-6-Palmitate or Tetrahexyldecyl Ascorbate are oil-soluble, which means they can be used in oil-only (waterless) products. Our skin absorbs oils much better than water, so vitamin C esters penetrate skin easier than L-ascorbic acid, but they still need to convert into L-ascorbic acid in the skin.

  • Efficacy comparable to L-ascorbic acid;
  • Stable in a product - long lasting;
  • Good skin penetration;
  • Can be used at neutral pH - excellent for sensitive and irritation-prone skin;
  • Can be paired with bakuchiol and retinol;
  • May be used both in the morning and evening.
  • Has to convert into L-ascorbic acid in the skin - takes longer to see the results;
  • More expensive;
  • Rare - very few skin care products on the market contain oil-soluble vitamin C.
Skin type and vitamin C

If your skin type is oily, normal or acne-prone, you may benefit from using L-ascorbic acid in a lightweight and fast absorbing water-based serum.

If you have sensitive, dry or combination skin, opt for oil-soluble vitamin C to enjoy all the benefits without the risk of skin irritation. 

Best vitamin C products

Clinical trials show that cosmetic products containing 10% - 20% of L-ascorbic acid deliver benefits of vitamin C on the skin. Higher than 20% concentrations don’t show better results and cause skin irritation. Novelty forms of vitamin C like Tetrahexyldecyl Ascorbate can be used in much smaller amounts in the product (up to 10%) to deliver great results without causing skin irritation and retain their efficacy for much longer than L-ascorbic acid.

Seek products that contain both vitamin C and vitamin E. They work in synergy, boosting each other's antioxidant properties and stability. 

Deerieo Aurora restorative facial oil serum with Vitamin C, bakuchiol, Vitamin E and Coenzyme Q10 in a glass dropper bottle.

Deerieo Aurora facial oil serum contains a novelty form of Vitamin C (Tetrahexyldecyl Ascorbate) along with Vitamin E, bakuchiol and Coenzyme Q10 blended with precious plant oils for superior antioxidant, antiaging and anti-pollution action. Click here for more details.

How to layer vitamin C products

Layering vitamin C in your skin care routine will differ depending on the type you are using. 

Using L-ascorbic acid in a water-based product? Apply the serum before the face moisturiser. That helps to deliver the vitamin C into deeper layers of your skin.

If you are using an oil-based novelty form of vitamin C like Tetrahexyldecyl Ascorbate, Ascorbyl-6-Palmitate etc., apply the product after the face moisturiser. This will help your skin stay hydrated and enhance the delivery of active ingredients into deeper layers of the skin.

Deerieo infographic showing how to layer oil-soluble vitamin C in skin care routine part 1.
Deerieo infographic showing how to layer oil-soluble vitamin C in skin care routine part 2Vitamin C in the summer

Vitamin C is good for the skin all year round, so make sure to include it in your summer beauty routine as well. It helps to prevent sun damage to the skin, improves skin firmness by increasing collagen production and prevents sun pigmentation spots by inhibiting melanin overproduction.

Regardless of the type of vitamin C you are using, it’s very important to use sunscreen, especially in the summer when UV radiation is strongest and will make your skin more prone to irritation if you've applied vitamin C-containing skincare.


Vitamin C is a must-have ingredient for a radiant and youthful skin. I hope you enjoyed this blog and found it useful. Please leave a comment or ask any questions - we'd love to hear from you!


1. Firas Al-Niaimi, MRCP(UK)(Derm), Nicole Yi Zhen Chiang, MRCP(UK)(Derm). Topical Vitamin C and the Skin: Mechanisms of Action and Clinical Applications, J Clin Aesthet Dermatol. 2017 Jul; 10(7): 14–17. [PubMed]

2. Fitzpatrick RE, Rostan EF. Dermatol Surg. Double-blind, half-face study comparing topical vitamin C and vehicle for rejuvenation of photodamage 2002 Mar;28(3):231-6. doi: 10.1046/j.1524-4725.2002.01129.x. [PubMed]

3. Herndon JH Jr, Jiang LI, Kononov T, Fox T. An Open Label Clinical Trial to Evaluate the Efficacy and Tolerance of a Retinol and Vitamin C Facial Regimen in Women With Mild-to-Moderate Hyperpigmentation and Photodamaged Facial Skin. J Drugs Dermatol. 2016 Apr;15(4):476-82. PMID: 27050703.

4. The Derm Review Tetrahexyldecyl Ascorbate: The New Stable Vitamin C Ingredient – Everything You Want To Know About This New Oil-based Vitamin C03.30.21

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