Dr Ian Webster
Dr Ian Webster

Our Ultimate Guide to Vitamin C

Between brightening dark spots and helping to protect against UV damage, there’s a lot Vitamin C can do for your skin. But the type of Vitamin C you select, as well as how you use and store it, can significantly affect the results you will achieve with your skin.

Vitamin C is a potent antioxidant that brightens dark spots, smooths fine lines, and, importantly, scavenges free radicals from the environment, pollution, and UV radiation. Over time, those free radicals can damage the skin, leading to premature signs of ageing, and increase your risk for skin cancer. So protecting against UV damage with an antioxidant—and, of course, daily SPF—is important.

Vitamin C has multiple benefits to the skin from prevention, to repair to overall glowing skin.

Here are some of the key benefits:

• It assists in the formation of new collagen and to restore healthy protein fibres
• Provides antioxidant protection against environmental damage by defending from free radical activity
• Shields the skin from ageing and DNA damage caused by pollution
• Promotes skin repair and wound healing
• Brightens the skin and reduces uneven skin tone
• Improves hyperpigmentation by regulating melanocyte functioning
• Reduces redness (erythema) and has anti-inflammatory benefits

Now that we know this is an ingredient we all need to supplement in our skin regimen, we now need to navigate through all the different kinds of formulations and varieties available. Not all vitamin C products are created equal— some are stronger and have more efficacy than others and some can cause sensitivity. It is very important to choose the correct form of Vitamin C as they can vary in effectiveness, stability and tolerance levels. Also, their formulation, concentration, permeability and efficacy when used topically as a cream or serum on the skin.

Topical Vitamin C is a much-discussed and studied topic, with a diverse array of opinions as to the best form and this can be confusing.

The Purest Vitamin C (L-Ascorbic Acid)

L-Ascorbic Acid (LAA) is the most researched type of Vitamin C and is seen as the gold standard when it comes to Vitamin C because it is the purest form. It is multi-functional with its ability to protect, prevent and correct the skin when applied topically. In the past, it has been much maligned as being unstable but this is only true if it is not formulated correctly. I feel that correctly formulated, stable, L-Ascorbic Acid is generally the first choice when it comes to choosing Vitamin C.

It’s a potent antioxidant that offers both internal and external protection, if formulated correctly, its most defining features are its bioavailability (recognized by the skin) and its permeability – having the ability to penetrate directly into the dermis to stimulate collagen synthesis. Generally, esterified (derivatives) forms of Vitamin C first have to be converted to ascorbic acid in the cells before they can help to stimulate new collagen.

Besides its ability to enhance collagen production, L-Ascorbic Acid, when topically applied, has been shown to down-regulate the enzymes responsible for collagen degradation and to preserve existing collagen. It has been shown to be very effective in preventing and treating sun-damaged skin.

The formulation is everything when it comes to L-Ascorbic Acid, for this water-soluble form of Vitamin C to penetrate the skin and be bioavailable, it should be formulated at the correct acidic pH. For optimised penetration into the skin, it should be within 2.0- 3.5 pH range.

For meaningful levels to be delivered into the skin L-Ascorbic Acid should be at concentrations of between 10%-20%.

For meaningful levels to be delivered into the skin L-Ascorbic Acid should be at concentrations of between 10%-20%. Studies have shown that a daily application of 15% L-Ascorbic Acid, at a pH of 3.2, increased skin L-Ascorbic Acid levels 20-fold and tissue levels were saturated after 3 days.
Different products may contain a wide variety of concentrations of Vitamin C. In general, they range from below 5% all the way up to 30% and this ingredient can have different effects at those concentrations.

Those with dry or sensitive skin should only use a lower concentration (10% or below) or consider using a derivative which will be less irritating. Those with more oily skin or with pigmentation issues should use  higher concentrations as part of an everyday skincare routine. The same applies to those wanting to prevent premature ageing.

As L-Ascorbic Acid can be irritating to the skin, it should always be introduced at a lower percentage and stepped up according to your own skin’s tolerance levels and needs. The higher the concentration and the lower the pH, the more risk of irritation especially if your skin is sensitive or prone to rosacea. It is always sad to hear people say they are ‘allergic’ to Vitamin C but this is usually attributed to using the incorrect form or strength, or that it has been introduced to the skin too rapidly without building tolerance.

Research has proven that specific combinations of antioxidants, when effectively formulated, perform synergistically and provide far more superior results than single antioxidant formulations.

Bigger is not always better but in this instance, the more the merrier. Research has proven that specific combinations of antioxidants, when effectively formulated, perform synergistically and provide far more superior results than single antioxidant formulations. A good example is Vitamin E, a potent lipid-soluble antioxidant, which has been proven to increase the photo-protection effects of L-Ascorbic Acid. In turn, L-Ascorbic acid also helps to regenerate the oxidative form of Vitamin E, which is important for preventing oxidative damage in the lipid cell membrane. Research has shown that Ferulic Acid aids in both stabilisation of the L-Ascorbic molecule and achieving an acidity of a pH below 3.5.

L-Ascorbic Acid and Sodium Ascorbyl Phosphate are water-soluble, meaning they’re more likely to show up in products that are lighter and better suited to oilier skin.

Vitamin C Esters or Derivatives

Other stable, esterified forms of Vitamin C, especially the lipid-soluble types, can be more gentle on the skin so they should not be discounted for those with sensitive skin. A combination of L-Ascorbic Acid with Vitamin C esters can also be very effective. Let’s take a look at some of the popular derivatives a little more closely.

Sodium Ascorbyl Phosphate

Sodium Ascorbyl Phosphate is a salt of Ascorbic Acid (Vitamin C), which provides antioxidant protection.  It has also been shown in some studies that 1% SAP has a strong antimicrobial effect in reducing which P.acnes, as well as sebum oxidation and this form of Vitamin C, could be used as a co-treatment with other acne treatments.

Whereas, a popular Derivative Forms of Vitamin C Magnesium Ascorbyl Phosphate (MAP) would be a better choice for those with more sensitive skins, as it is not formulated in such a low acidic form that it causes irritation in more sensitive skins.

Magnesium Ascorbyl Phosphate

A non-irritating, stable, ascorbyl ester of Vitamin C. This lipophilic molecule is easily absorbed into the skin, has hydrating effects and helps to decrease transepidermal water loss. It is a free radical scavenger, it helps to improve skin elasticity, boosts collagen synthesis and helps to reduce photo-damage. It also promotes wound healing and suppresses melanin formation at significantly lower concentrations than L-Ascorbic Acid.

Ascorbyl Glucoside

In general, Ascorbyl Glucoside is also a popular derivative because this is a less potent version of vitamin C, it’s a good option for all skin types. Ascorbyl Glucoside, which is a noticeably more stable, gentler take on Vitamin C. It is a Vitamin C precursor and is converted into ascorbic acid thus because it’s undergone a conversion process, it’s much less likely to cause irritation. It protects melanin from oxidation and contributes to excess melanin removal by increasing cellular renewal. It has a lightning and brightening effect and helps to protect the cells from harmful UV radiation.

If you have dry, mature skin, you are looking for more moisturising products containing lipid-soluble forms of vitamin C, like Tetrahexyldecyl Ascorbate and Ascorbyl Palmitate.

Tetrahexyldecyl Ascorbate

A stable, oil-soluble form of Vitamin C is used in skincare products and sunscreens. It works well when used together with other forms of Vitamin C in anti-ageing products.

There is some discussion around whether it is more potent than L-Ascorbic Acid, because it is oil-soluble and able to penetrate the lipid layer into the dermis. However, studies show that if                L-Ascorbic acid is correctly formulated according to strict parameters it is equally able to penetrate into the dermis.

Vitamin C is generally pretty safe and well-tolerated but if you have sensitive skin, L-Ascorbic acid might be prickly or irritate the skin as it is an acid so then it would be best to lower your concentration or use a more gentle derivative.

What Dr Webster Suggests

To minimise the risk of stinging/prickling when using an acidic Vitamin C product, make sure the cleanser you use beforehand is a neutral pH cleanser. It is best to rinse off the cleanser pat dry and wait a minute or two before applying the Vitamin C product. You do not want to use an alkaline soap (+-pH10) followed by an acidic Vitamin C product.

The one ingredient you should steer clear of when using vitamin C is Benzoyl Peroxide, which can oxidise the Vitamin C and, therefore, make it less potent. You can still use your benzoyl peroxide products, just not at the same time in your routine as the Vitamin C. Try using Vitamin C in the morning and Benzoyl Peroxide in the evenings, or use them on different days.

In the past it was thought that you should avoid using Vitamin C products with Retinoids at all costs. Using them in the same part of your routine can cause irritation, but it’s okay to use them on the same day at different times. Experts generally advise using vitamin C products in the morning and retinoids at night. You do find them sometimes formulated together in a multi-functional product but then the concentrations are often lower.

Vitamin C is vulnerable to light and heat and if not stored correctly it can oxidise rapidly. It should always be packaged in a dark, opaque container and exposure to air should be limited. It should be stored in a dark, cool, dry place, away from any form of sunlight or heat which can both degrade the product.

Don’t limit yourself to serums.

The most common way to get Vitamin C in a skin-care routine is in a serum form, but recently encapsulated or ampoule-based serums are becoming a popular choice of formulation, as single-use capsules or ampoules protect the serum from degradation by light, air, and water.

However, you don’t have to limit yourself! If you’d rather not add an extra step to your regimen, know that you can also get Vitamin C in cleansers, moisturisers, and even sunscreens.

It is important to note that the human skin has low permeability and any Vitamin C, in whatever form, must be able to penetrate the skin’s outer layer, the stratum corneum, for delivery into the dermis where collagen synthesis can take place. Only then will meaningful changes take place on the skin.

Reference: J Clin Aesthet Dermatol. 2017 Jul: 10(7): 14-17

Posted in LEARN / INGREDIENT FOCUS on June 7th, 2018. / Updated: September 2020

Posted in LEARN / INGREDIENT FOCUS on June 7th, 2018.

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