Skin school, Anti-aging, Serums, Skincare

Vitamin C serum L-Ascorbic Acid (LAA)

vitamin c serum
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What is 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).

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 effect of the sun. Think of it as more of a ‘booster’ that assists your sunscreen.

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 other products are applied. If you use a pH-adjusting toner after cleansing, allow enough time to completely dry on the skin before applying Vitamin C Serum. If using a higher pH cleanser, allow 15 minutes afterward to allow 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 will need to 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 level of oxidation.

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 fine with being stored in the fridge, but some companies out there 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 ameliorate 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.


[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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