Mythbusting: Are Vitamin C Serums Bad for You?

Mythbusting: Are Vitamin C Serums Bad for You?

I’ve been asked a lot for my opinion on a recent article on whether vitamin C serums are bad for your skin. In the article, Wendy explains why Oumere will never have a vitamin C serum in their line. She outlines that vitamin C can:

  • Act as a pro-oxidant when it reacts with iron in the air (or iron and copper in cosmetics) via the Fenton reaction, leading to irritation, collagen and elastin breakdown and acne
  • Lead to desensitisation (tachyphylaxis) so if you start using it too young, your skin won’t respond later on

Let’s take a look at both of these arguments.

Is Vitamin C Pro-oxidant?

While in some circumstances vitamin C can act as a pro-oxidant after it reacts with metals and potentially lead to collagen destruction, vitamin C is also known to have effects that are the exact opposite:

  • Vitamin C on its own is a potent antioxidant that soaks up free radicals and prevents the oxidative damage that results from UV light and other environmental stressors, as well as normal biological processes
  • Vitamin C is an essential cofactor that’s required for enzymes that crosslink and stabilise collagen (prolyl and lysyl hydroxylase)

Mythbusting: Are Vitamin C Serums Bad for You?

So how do we tell which of these actions, pro-oxidant or antioxidant, wins out? Science, of course! More specifically, we have quite a lot of clinical trials on vitamin C where vitamin C serums are applied to actual human skin, and its effect is measured. Vitamin C is one of THE best researched skincare ingredients.

None of the clinical trials on topical vitamin C (that’s vitamin C applied to the skin) found a decrease in collagen. In fact, a whole bunch of studies found that vitamin C increased collagen. In these studies, the volunteers were also exposed to air pollution and other cosmetic products, which were proposed to be the sources of metals that would cause a pro-oxidant effect in the article. Clearly the antioxidant effect is winning.

Related Post: Antioxidants in Skincare: What Do They Do?

Studies where vitamin C increased collagen:

Most studies on vitamin C measure its effect on photodamage. These studies generally measure the effect of vitamin C on wrinkles. While this isn’t a direct measure of collagen, lack of collagen causes deeper wrinkles, so if vitamin C was having a pro-oxidant effect you’d see a worsening of photodamage (which is actually caused partially by increased oxidation). In these studies, vitamin C improved photodamage:

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Why Vitamin C Can Stain Your Skin (and How to Avoid It!)

Why Vitamin C Can Stain Your Skin (and How to Avoid It!)

Vitamin C is one of the few skincare ingredients with a ton of independent research to back up its properties, like its brightening and anti-wrinkle benefits. Those of you who are vitamin C enthusiasts may have noticed that with some vitamin C serums, you end up with slightly stained orange-brown skin after a few days of use – sort of like fake tan. I’ve often wondered why but didn’t really dig into it past a quick Google search (which found nothing), so I just put it off as a weird side effect of vitamin C oxidising.

But recently, I came across a diagram in a peer-reviewed paper on a completely different topic that accidentally told me exactly why vitamin C does this: ascorbic acid eventually oxidises to erythrulose!

Why Vitamin C Can Stain Your Skin (and How to Avoid It!)

As most of you may know, vitamin C in the form of ascorbic acid oxidises easily to dehydroascorbic acid, which has an orange-brown colour. It does this when it’s stored in water, as well as on your skin. Oxygen and light exposure will speed up the oxidation reaction. This reaction is reversible, so you can get back the ascorbic acid if you have the right antioxidants in the formula.

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The Ordinary Skincare Review Pt 1: Lactic Acid, Advanced Retinoid

The Ordinary Skincare Review Pt 1: Lactic Acid, Advanced Retinoid

Unless you’ve been living under a rock or just aren’t that into skincare, you’d have heard of The Ordinary by now. The newest brand from Deciem (parent company of NIOD and Hylamide) aims to bring effective skincare to the market at affordable prices.

As a skincare science nerd, it’s very exciting because many evidence-backed ingredients are very cheap, but skincare brands often price the products containing them at a premium because they work so well, and everyone else prices them high.

While some expensive brands do incorporate other technologies in their formulations that would justify the higher price, it’s really annoying as a consumer. You never know for sure how well a specific product will work for you, and no one wants to spend $70 on a product just to find out that it does nothing for your skin three months down the track. All of The Ordinary’s products are priced between $8.80 and $24.90, and you can get them online, or in-store at Myer, Priceline or the standalone Deciem stores.

The products are very plainly named according to what ingredients they contain. Interestingly, they don’t really emphasise what each product is supposed to do, so it seems like they’re targeting this line towards skincare nerds who know what they want. It makes sense,since most of the formulas contain only one or two star ingredients and are well-suited to multi-step routines, unlike the “multivitamin”-like all-in-one products aimed at a less obsessive audience who aren’t as interested in hardcore customisation.

The Ordinary Skincare Review Pt 1: Lactic Acid, Advanced Retinoid

I’ve trialed 4 products so far: Lactic Acid 10% + HA 2%, Advanced Retinoid 2%, Niacinamide 10% + Zinc 1% and  “Buffet”. I’ll be talking about the first two in this post, and the second two in a post later this week. But before we delve into each individual product, here are some general remarks:


All 4 products come in 30 mL droppers, which I like because it’s easy to measure out the right amount of product, but it isn’t as convenient as a pump (dropper bottles also let in more light and air than airtight pump dispensers, but I don’t think it’s an issue with these particular products – more on that later).

One annoying thing with droppers is if the product is thick and you’re not careful when replacing the dropper, the product on the dropper scrapes off onto the neck of the bottle, and you get lots of caked up product on the threads. This luckily hasn’t a problem with these products since they’re quite runny, but I’ve experienced this a lot with liquid illuminators. The labels are no-nonsense and monochromatic chic.

Excluded Ingredients

All Deciem products are free of parabens, sulphates, mineral oil, methylchloroisothiazolinone, methylisothiazolinone, animal oils, benzalkonium chloride, coal tar dyes, formaldehyde, mercury and oxybenzone, and are not tested on animals. All four The Ordinary products I’m reviewing here are alcohol-free, silicone-free, nut-free and vegan.

There isn’t evidence that all of these ingredients are harmful (parabens are safe, as is mineral oil). Silicone is a bit annoying in routines because it can make other products roll off your face, and alcohol can be drying, so it’s convenient that these products have been formulated without them. There’s specific information on each product on the website, which is handy if you have nut allergies or if you want to stick to vegan products.

The prices I’m giving here are the Australian retail prices.

Lactic Acid 10% + HA 2%

Price: $12.70 for 30 mL (prices vary on Amazon)

Good for: exfoliation, hyperpigmentation, congested skin, fine lines

Contains lactic acid: Lactic acid is an alpha-hydroxy acid that’s fantastic for chemical exfoliation, and due to its slightly larger size, is supposed to be less irritating than glycolic acid. This is a particularly good option for people who are prone to post-inflammatory hyperpigmentation (i.e. anyone with dark skin or hair, including light-skinned Asians). In Australia (and most other places), glycolic acid products outnumber lactic acid products 20 to 1, so this is a very welcome addition to the market.

pH: Lactic Acid 10% + HA 2% has a pH of 3.60-3.80, according to The Ordinary’s website, which is low enough to be effective. The Ordinary’s site states that a higher pH would be more irritating. I’m not sure what the reasoning for this is, since lower pH is both inherently more irritating, and allows more acid to get into the skin and exfoliate…

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