Skin school, Anti-aging, Serums, Skincare

Vitamin C Serum L-Ascorbic Acid (LAA)

Vitamin C is a powerful skin-brightening and anti-aging ingredient!

vitamin c serum LAA

written by Emma Wilson

updated on

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Pure Vitamin C (L-ascorbic acid) is one of the most potent skincare ingredients for improving the appearance of fine lines and wrinkles, fading hyperpigmentation, protecting against photo-aging and pollution, and treating acne scarring! It’s one of the most thoroughly researched skincare ingredients, and dermatologists agree it is one of the most effective ingredients to include in your skincare routine.

What Is a Vitamin C Serum?

Vitamin C Serums are most commonly made with L-Ascorbic Acid (LAA), the active ingredient I will write about today. Serums typically have higher concentrations of LAA when compared to their cream/lotion-based counterparts. When starting out using a vitamin C serum, it is a good idea to gradually increase usage from a lower percentage (10%) and application times (1-2 days) to higher percentages (15-20%) and more frequent application (2x daily).

The Importance of Vitamin C in the Body

All animals naturally use vitamin C to protect themselves from oxidative damage, synthesize collagen, heal wounds, and perform many other vital bodily functions. Vitamin C is an essential vitamin that animals cannot survive without. For example, a lack of vitamin C in most animals results in scurvy.

Some animals, such as ruminants, can synthesize vitamin C from monosaccharides within the body. However, humans (and other primates), guinea pigs, invertebrates, some insects, fish, bats, and birds cannot synthesize vitamin C as they lack an essential enzyme called L-gluconolactone oxidase.

Therefore, Vitamin C is an essential part of our diet and is absorbed in our small intestines when we eat citrus fruits and green leafy vegetables.

The Role of Vitamin C in the Skin

Just as vitamin C is necessary to perform critical biological functions throughout the body, it is also an essential ingredient in our skincare routine. This is because our skin requires vitamin C to synthesize collagen and to inhibit the overproduction of elastin following UV exposure. As you might already know, collagen and elastin are two critical fibrous components of the dermis, the dermal layer of our skin. Together, they maintain the supportive structure of our skin, giving it both firmness and elasticity.

Unfortunately, as we age, our skin becomes thinner and more fragile because the collagen and elastin structures begin to break down. Lifestyle and genetics contribute to the rate at which these fibrous proteins break down. However, it’s typically said that our skin produces about 1 percent less collagen each year after age 20. I did the math, meaning my skin already has 15% less collagen than when I was 20 years old!

How Does Vitamin C Help Prevent Skin Aging

Although skin aging is a natural process that we can’t stop from happening, using antioxidant ingredients such as vitamin C in our daily skincare routine can help slow this process down.

Research has shown that L-ascorbic acid quickly penetrates the dermis layer of our skin (where it’s needed) due to its small molecular size and water solubility.

Studies have found that topically applied L-ascorbic acid at concentrations between 5 and 15% has a skin anti-aging effect by:

  • Increasing the production of collagen types I and III
  • Preventing the inactivation of enzymes which stabilize the three-dimensional structure of collagen
  • Inhibiting the enzyme collagenase 1 (which is one of the enzymes that break the peptide bonds in collagen)
  • Neutralizing and removing oxidants found in environmental pollutants
  • Neutralizing and removing oxidants found after exposure to ultraviolet radiation (thereby preventing photo-aging)

In addition, vitamin C has also been shown to prevent hyperpigmentation (starting at concentrations of 10%) by inhibiting the enzyme tyrosinase (which is necessary for the synthesis of melanin). However, although vitamin C has been shown to prevent hyperpigmentation, it hasn’t been shown to treat hyperpigmentation that already exists on the skin.

Does My Skin Already Contain Vitamin C?

Yes, our skin already contains vitamin C which, as I mentioned, is absorbed in the small intestine from our fruits and vegetables. Although no studies have been conducted on the relationship between the levels of vitamin C in our diet and the aging of our skin, more generalized nutritional studies have found that diets higher in antioxidants are associated with improved measures of skin elasticity, facial wrinkling, roughness, and color.

This suggests a diet rich in fruits and vegetables can benefit skin health. However, it’s challenging to determine which active component in the fruit and vegetables is responsible for the observed benefit to the skin. The observed effect from these studies is likely to be multifactorial, not only a result of vitamin C in the diet.

There is also a question of how stable vitamin C serums are (since ascorbic acid is a highly unstable compound and quickly oxidizes when exposed to oxygen, light, or heat). Knowing what to look for in a vitamin C serum is imperative.

So Should You Buy A Vitamin C Serum, or Is It A Waste of Money?

If you have a healthy diet, full of fruits and vegetables high in antioxidants, then your skin should contain enough vitamin C to function the same way a topical vitamin C serum would function. So, is your money better spent on other skincare products?

I spent a lot of time digging a little deeper into this. I found many testimonials from people in their 50s and 60s who saw considerable skin improvements when using a long-term vitamin C serum (generally longer than three months). I also found the same age group commenting that their skin became easily pigmented with dark spots when they stopped using a vitamin C serum.

This could be explained by the evidence that as we age, the level of vitamin C in our skin declines in both the dermis and epidermis and that sunscreen only blocks 55% of the free radicals produced by UV exposure! Pollutants such as smoke and exhaust fumes also lower vitamin C content (especially in the epidermis). We all know that smoking cigarettes causes our skin to age faster. One of the reasons is that smokers have been shown to have depleted vitamin C levels compared with non-smokers.

So, although it’s a hot debate whether a vitamin C serum is necessary if you’re already getting enough vitamin C through dietary intake, I do think that people with mature skin could benefit from the UV-protective effects of a quality vitamin C serum (especially if you get excessive sun exposure like me here, in Australia).

What Does Vitamin C Serum Do?

Vitamin C Serum is one of the few products that will deliver what it promises on the box. Remember that it can take several months (6+) before results are fully realized.

  • Rich antioxidant properties repair and renew the cells to give skin a healthier look;
  • Facilitates the creation of collagen in the skin, which produces tighter and firm skin;
  • Vitamin C is ideal for the treatment and prevention of the onset of wrinkles;
  • Manages and removes free radical damage on the skin. Post-inflammatory hyperpigmentation (PIH) can be reduced with the use of LAA;
  • Vitamin C does not replace your sunscreen. It thickens the dermis layer of the skin, which helps prevent the harmful effects of the sun. Think of it as more of a ‘booster’ that assists your sunscreen.
The Best Korean Vitamin C Serums with Pure L-Ascorbic Acid
Best Korean Vitamin C Serums with L-Ascorbic Acid in 2023 by Adela Wong for Garden of Muses

How Do You Use Vitamin C Serum, and Where in My Routine Do I Use It?

LAA Vitamin C Serums are best used on clean skin before applying other products. If you use a pH-adjusting toner after cleansing, allow enough time to completely dry the skin before applying Vitamin C Serum. If using a higher pH cleanser, allow 15 minutes afterward for your skin to return to an average pH level before applying Vitamin C Serum.

How much product you use will vary for each person and each product. This will be something each individual will need to experiment with and find out what works with their skin.

Take your serum, and use your clean fingers or a cotton pad to spread it over your face. Your skin should fully absorb the product. If you end up with a film on your skin, you must reduce the amount of serum used. Allow 15 minutes after application for your skin to absorb the serum before moving on to the next step in your routine.

To make this simple: Cleanser>Vitamin C Serum>pH Dependant Acids>Rest of Routine.

Remember that you can use your BHA/AHA products before your Vitamin C Serum, though it may reduce the efficacy. This is a personal choice regarding how you layer your pH-dependent products with Vitamin C Serum.

vitamin c serum benefits

What Color Should My Vitamin C Serum Be?

Vitamin C Serums are usually clear or tinted, similar to champagne. When your serum changes begin to yellow and eventually brown, it is a tell-tale sign of oxidization. Some companies add dye into their serums that darken the color, though I would be wary of such formulas as this could hide oxidization.

Do I Still Want to Use It If It’s Changed Colors (Oxidized)?

When Ascorbic Acid oxidizes, it changes to dehydroascorbic acid (DHAA), which changes the color of your serum from that clear-champagne tone down to a deep brown/red based on the oxidation level.

Is DHAA harmful to the skin itself? No. Using a serum with slight yellowing isn’t as bad as it’s made out to be, though it may irritate your skin due to the higher concentrations of DHAA. If your serum has changed to a dark color, I suggest not using it due to the high probability of irritation.

How Should I Store My Vitamin C Serum?

Because LAA is highly susceptible to oxidization from light, oxygen, and temperature, it is best kept in a dark-colored container that is mostly (or even entirely) opaque. Vitamin C Serum should be kept in a cool dark place, like a potato! Most serums are OK with storing in the fridge, but some companies advise that their products should not be refrigerated (Paula’s Choice C15).

Why Is My Skin Orange?

Applying too much serum to your skin can leave a slight film that is not absorbed. If you are not careful, this residue can oxidize and turn your skin into a lovely shade of Oompa-Loompa. The best way to avoid having this effect is to use less product and wash your hands after application.

What Other Ingredients Does It React To?

Vitamin C and niacinamide

You will occasionally hear about niacinamide when the topic of Vitamin C Serums comes up. So what will happen when you use both? When both products are mixed, both compounds become useless and can cause the skin to flush because of the reaction. If you are compelled to use the two ingredients together, try to use them at night and wait 30 minutes between applications so the skin’s pH may return to an average level and limit the interaction between the two compounds.

Vitamin C and tretinoin

vitamin c LAA with tretinoin

Recent studies show that combining tretinoin and vitamin C produces a stable and effective skincare solution [9]. They both work together to alleviate skin aging.

This beneficial duo should maybe be put aside when first starting tretinoin. It is advisable to stop all actives when starting tretinoin to avoid irritation. Yes, even if prior use was not eventful. 6 months in, when the skin is accustomed to the prescription medication, vitamin C can be re-introduced.

Show Me Proof

[1] “Accumulation of Vitamin C (Ascorbate) and Its Oxidized Metabolite Dehydroascorbic Acid Occurs by Separate Mechanisms (*).” Accumulation of Vitamin C (Ascorbate) and Its Oxidized Metabolite Dehydroascorbic Acid Occurs by Separate Mechanisms. Accessed September 22, 2014. .

[2] “Journal of Nutritional Science and VitaminologyVol. 54 (2008) No. 4 P 315-320.” Vitamin C Activity of Dehydroascorbic Acid in Humans —Association between Changes in the Blood Vitamin C Concentration or Urinary Excretion after Oral Loading—. Accessed September 22, 2014. .

[3] “Photochemical Interaction of Ascorbic Acid with Riboflavin, Nicotinamide and Alpha-tocopherol in Cream Formulations.” – Ahmad. Accessed September 22, 2014. .

[4] “ReCverin Absorption Study PDF.pdf – Microsoft Word Online.” ReCverin Absorption Study PDF.pdf – Microsoft Word Online. Accessed September 22, 2014.!115&ithint=file,pdf&app=WordPdf&authkey=!AFHfRMwGlGorzcc .

[5] “Result Filters.” National Center for Biotechnology Information. Accessed September 22, 2014. .

[6] “Revitalizing Aging Skin with Topical Vitamin C – Life Extension.” Accessed September 22, 2014. .

[7] “Should Niacinamide and L-Ascorbic Acid Be Used Together? – FutureDerm.” FutureDerm. Accessed September 22, 2014. .

[8] “Solution Phase Interaction of Nicotinamide with Ascorbic Acid.” – Guttman. Accessed September 22, 2014. .

[9] Gianeti MD, Gaspar LR, Camargo FB Jr, Campos PM. Benefits of combinations of vitamin A, C and E derivatives in the stability of cosmetic formulations. Molecules. 2012 Feb 22;17(2):2219-30. doi: 10.3390/molecules17022219. PMID: 22357318; PMCID: PMC6268122.

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