Philippine Dermatological Society

VITAMIN C IN SKINCARE: WHAT YOU NEED TO KNOW

Dr. Mara Padilla Evangelista-Huber, FPDS, FDSP, MClinRes

Why use vitamin C in your skincare routine?

Vitamin C is one of the most popular active ingredients in the skin, and for good reason! It has multiple beneficial effects.

First, it is a powerful anti-oxidant that protects us from free radicals – substances that can damage our skin cells and cause premature skin aging.

It also has photoprotective effects, shielding us against the damaging effects of the sun’s rays on skin, which include wrinkles, dark spots, rough skin texture and many more.

Vitamin C can also increase collagen production, keeping skin plump and improving skin elasticity and texture.

Lastly, it inhibits tyrosinase, a key enzyme in the production of melanin (the pigment responsible for our skin color), which makes it helpful for fading hyperpigmentation and brightening overall skin tone.

Topical vitamin C products are not created alike.

One of the most important factors that determine how your vitamin C product will work is the type of vitamin C in it. L-ascorbic acid (LAA) is the active form of vitamin C in skin, and is the most effective based on clinical studies. Unfortunately, LAA can be irritating due to the low pH of the formulation, and is also the most unstable among the vitamin C types.

Vitamin C can be found in different topical skincare products, but a serum is likely the most efficient preparation for LAA. A serum can deliver a high concentration of active ingredients, and, particularly for LAA, a serum preparation can keep pH at the desired range (3.5 or lower) so the active remains stable. Derivatives of LAA may be compatible with other vehicles due to a higher pH of the formulation.

Packaging and storage matters with vitamin C products.

 Despite the many advantages of vitamin C, its main disadvantage is that it is highly unstable. It rapidly oxidizes in the presence of light, heat, other metal ions, and changes in pH into a chemical known as dehydroascorbic acid (DHAA), which results not only in a change of color (brassy brown), but a loss of efficacy, too.

Vitamin C product characteristics that increase shelf life:
  1. Air tight packaging, such as those with pumps
    – Thinner serums often come in bottles with droppers which may increase exposure to air, which leads to oxidation. Purchasing fewer quantities will help reduce product wastage.
  2. Dark-tinted packaging (e.g. dark, opaque bottles)
  3. Formulations with vitamin E (tocopherol), ferulic acid, other antioxidants
How to store your vitamin C product:
  1. Store it in a cool, dark place. Avoid leaving anywhere exposed to direct sunlight.
  2. Be aware of the expiration date. Dispose when expired.
  3. Close the bottle tightly after use.
Vitamin C derivatives

These non-LAA vitamin C types should be able to penetrate into skin cells and chemically convert into LAA to exert effects. These LAA derivatives are more stable, less sensitizing due to higher pH, but are generally less effective. Here are some examples of non-LAA vitamin C:

Tetrahexyldecyl ascorbate
3-o-ethly ascorbic acid
Ascorbyl glucoside
Magnesium ascorbyl phosphate

Sodium ascorbyl phosphate
Ascorbyl tetraisopalmitate
Ascorbyl palmitate

Among these, tetrahexyldecyl ascorbate is supported by the most research, while ascorbyl esters (palmitate) have the least amount of research, and may potentially lead to paradoxical lipid oxidation which can cause skin damage.

When should I use my vitamin C product?

You may apply your vitamin C product either in the morning or the eveningConsistency is key, so it’s best apply the product at a time you believe is practical and sustainable for you.

How often should I apply my vitamin C product?

While some vitamin C formulations require once daily applications, others with lower concentrations may be used twice daily. Follow the directions in the product label.

What ingredients should not be used with my vitamin C product?

There is no hard and fast rule that says what ingredients you should not use with vitamin C as individuals vary in their skin types and tolerance. That being said, there is always a potential for reactions when multiple potentially irritating active ingredients are used in the same routine, e.g. alpha- and beta-hydroxy acids, vitamin A derivatives (e.g. retinoids, retinol), benzoyl peroxide, etc.

When using other potentially irritating actives in your skincare routine, it is a good idea to use them at different times to decrease the chance of developing skin reactions, i.e. using vitamin C during the day then tretinoin at night.

What ingredients work well with my vitamin C product?

Ingredients that work best with vitamin C are those that complement its effects and increase its stability.

Vitamin E and ferulic acid support the anti-oxidant effects of LAA and make it more stable. The presence of other anti-oxidants (e.g. green tea) and hydrating ingredients (e.g. hyaluronic acid) are helpful too! Sunscreens complement vitamin C’s effects well.

Other vitamin C tips:
  1. Patch test before use.
  2. Start from a concentration of 10% or lower.
  3. Start low and go slow: may use thrice a week at the start and increase to daily use as tolerated.
  4. Best to apply product directly on skin as possible, before other leave-on products.
  5. Hold products with other active ingredients until you have determined vitamin C is suitable for your skin.
  6. Be aware if you are experiencing side effects (e.g. irritation, stinging, burning). You can always pick another active – there are many other choices!
References:

Telang PS. Vitamin C in dermatology. Indian Dermatol Online J. 2013;4(2):143-146.

Levin J, Momin SB. How much do we really know about our favorite cosmeceutical ingredients? J Clin Aesthet Dermatol. 2010 Feb;3(2):22-41.

Burke KE. Interaction of vitamins C and E as better cosmeceuticals. Dermatol Ther. 2007. Sep-Oct;20(5):314-21.

Lin FH, Lin JY, Gupta RD, et al. Ferulic acid stabilizes a solution of vitamins C and E and doubles its photoprotection of skin. J Invest Dermatol. 2005 Oct;125(4):826-32