I was really excited to finally get my hands on a bottle of O.S.T. Vitamin C20 Serum. It’s been on my wish list for a long time. I’m a big fan of Vitamin C as a skin care ingredient in general, but stopped using it last year when I started using tretinoin (generic Retin-A). It’s generally advised not to mix tretinoin and Vitamin C in a single routine, though, if your skin isn’t sensitive (and you’re not spending a lot of time outdoors), it can be okay to use Vitamin C in the morning and tretinoin at night. It took a while for my skin to get used to the tretinoin, and my skin was very sensitive during that time; I just didn’t think my face could handle both. My skin is now used to the tretinoin, and I just switched to the micro-gel version (which I find to be much gentler), so when I had the opportunity to try this serum, I said, “Get on my FACE, Vitamin C!” Okay, I didn’t say that. But I thought it, and I still think it every morning, as I’m applying this serum.
What is it?
O.S.T. Original Pure Vitamin C20 Serum ($25) is a Vitamin C powered serum that claims to exfoliate, brighten skin, fade acne scars/post-inflammatory hyperpigmentation (PIH), and remove blackheads.
Water, Ascorbic Acid, Ethanol, Sodium Lactate, Butylene Glycol, Glucose, Camellia Sinensis Leaf Extract, Rosa Davurica Bud Extract, Carthamus Tinctorius (Safflower) Extract, PEG-60 Hydrogenated Castor Oil, Sodium Hyaluronate, BIS-PEG-18 Methyl Esther Dimethyl Silane, Diethoxyethyl Succinate, Ammonium Acryloyldimethyltaurate/VP Copolymer, Xanthan, PEG-180, Gluconolactone, Beta-Glucan, Citrus Aurantium Dulcis (Orange) Oil, Zinc PCA, Panthenol, Niacinamide, Glycerin, Tocopherylacetate, Lecithin, Caprylic/Capric Triglyceride, Ubiquinone, Diisopropyladipate, Phenoxyethanol, Methylparaben
The ingredient list looks okay at first glance, as this serum does contain a multitude of good skin care ingredients. There are also some things about this ingredient list that I find confusing, but I’ll get to that in just a minute. First, the highlights:
Ascorbic Acid – Ascorbic acid is the source of Vitamin C in this serum, and it accounts for 20% of the serum. As a general rule, you want at least 10% for an effective formula, 15% is better, and 20% is pretty great. Topical Vitamin C has been scientifically proven as an effective topical treatment for a variety of skin conditions, including acne, reduction in photodamage, fading of scars, and strengthening the skin’s barrier function. It also promotes collagen production, and is often marketed as an anti-aging ingredient for this reason.
Unfortunately, Vitamin C in general is not very shelf stable. It’s extremely sensitive to light and oxygen; overexposure to either one of those things will cause it to oxidize rapidly, at which point it loses its efficacy. This is why it’s important for Vitamin C to be packaged in dark colored or opaque bottles – a clear bottle would render the product ineffective fairly quickly. It’s also important to use up a Vitamin C product within a a reasonably short span of time – 3 months is a good rule of thumb, but if your Vitamin C product darkens at any point, it’s time to stop using it. A darker product means it has oxidized.
There are many different sources of Vitamin C; Ascorbic Acid (which also happens to be an AHA) only represents one of them. Unfortunately, it’s not the best choice to be used topically. It’s effective, but it is a little less stable, and it is more likely to cause irritation than other C sources such as C-ester or magnesium ascorbyl phosphate (MAP).
If you’re interested in reading just a small sampling of the scientific studies surrounding Vitamin C as a skin care ingredient, here are some good places to start:
Sodium Lactate – Sodium Lactate is a sodium salt derived from Lactic acid. It’s a highly effective antimicrobial agent . In fact, it’s often used as a preservative in meat and poultry products for precisely this reason. As a skin care ingredient, it also has exfoliating properties and works well as a pH adjuster.
Camellia Sinensis Leaf Extract – Better known as Green Tea Extract, this ingredient is a highly effective antioxidant and anti-inflammatory ingredient.
Sodium Hyaluronate – Often referred to as hyaluronic acid, this ingredient is able to hold up 1,000 times its weight in water. This humectant also does a great job attracting and maintaining water in the skin, and promotes blood circulation and nutrient absorption.
Niacinamide – This is a cell-communicating, anti-inflammatory ingredient that has been proven in numerous studies to increase barrier function and ceramide levels, and lightens hyperpigmentation. It’s one of my all time favorite actives!
However, I am a bit confused about Niacinamide’s presence in this formula, as it is typically known to be incompatible with Vitamin C, especially in the form of Ascorbic Acid as it appears in this serum. Niacinamide and Vitamin C cancel each other out when mixed with one another in water-based solutions – which is what this serum is. Because Niacinamide is so low on the list of active ingredients in this formula, I’m guessing it’s not present enough to cancel out the efficacy of the Ascorbic Acid, but I am wondering what its role is in this serum. If any cosmetic formulators happen to be reading this and can shed some light on why Niacinamide is included in this formula, I’d love your insight!
Ubiquinone – Better known as CoQ10, Ubiquinone is an antioxidant that can help increase collagen production when present in large enough amounts. Ubiquinone is pretty low on the ingredient list in this particular formula, however, so once again, I find myself asking why it’s been included.
It’s worth mentioning that this formula also contains alcohol (which appears as “Ethanol” in the ingredient list). The alcohol is the only major red flag in the O.S.T. Vitamin C20 Serum according to COSDNA, where the ingredient ranks a 3 out of 5 as a potential irritant. I’ve mentioned here before that there are a large number of people who believe that alcohol is harmful to the skin in any amount and in any formula. There is also a line of thought that when included in a well-formulated product, it is a beneficial ingredient because it increases the absorption of other skin-healthy ingredients. Based on the research available, which is best summed up in this FutureDerm article, I’m personally inclined to fall into the “alcohol can be good in a well-formulated product” side of the great debate.
The O.S.T. Original Pure Vitamin C20 Serum arrives in a well-sealed, amber glass bottle. The dark colored glass is a good choice for helping to prevent product oxidation. It comes with a glass dropper cap, which is packaged separately to prevent it from breaking during shipping. I would have preferred to see this product in an airless pump to prevent air exposure, but a dropper is fine – it would be my second choice.
This serum smells delightfully like fresh oranges.
Before I get into my application method, I’d like to point out that the O.S.T. Vitamin C20 Serum really is designed to be used at night. The primary reason for this is its Ascorbic Acid content, which is easily broken down by UV rays. That said, I use this product during the day because I’m a nightly Tretinoin user, and the two products aren’t compatible. However, I am very vigilant about wearing sunscreen, and most days I get very little sun exposure – 22 minutes total for my drive to and from work. I skipped this serum on a couple of occasions when I knew I would be outside or in the car for a while.
As for my application method, I apply this serum as soon as I dry my face after cleansing in the morning. In a typical Asian skin care routine, this would actually be the serum step, which comes after the toner, but back when I was using the Perricone MD Vitamin C product, I applied my C first thing after cleansing. That worked well for me, so I decided to use this in a similar manner. I follow up with my facial oil, my sunscreen, an essence, and my moisturizer.
Before trying this serum, I read a few blog reviews that stated this serum dries with a sticky finish. If you apply this serum on its own and don’t apply any additional skin care products afterward, that is 100% true. This serum glides on during application, but it does feel sticky to the touch once it’s dry. However, there is never a situation when I’m applying this serum on its own – well, except for the instance when I did it for the purpose of learning if it really is sticky. Once I apply my subsequent skin care products, there is absolutely no trace of stickiness.
Also worth mentioning is that the O.S.T. Vitamin C20 Serum does tingle a bit just after application. I can’t tell if it’s the alcohol, the Ascorbic Acid, or a combination of both that’s causing the sensation, but it’s definitely there. It’s not unbearable – in fact, I wouldn’t even call it painful. It’s just slightly uncomfortable for a minute or so after application.
There are a few things I wish I could change about this serum: I wish it didn’t contain Niacinamide because of its incompatibility with Ascorbic Acid, and I wish it didn’t cause any sensation when I apply it. If I had my way, I would also probably forego the alcohol in this formula, even though I’m not entirely averse to alcohol as an ingredient in the right product.
All that said, my results from using the O.S.T. have been spectacular! When I began using this serum, I had some very visible hyperpigmentation spots on my right cheek that had been lingering for weeks with little to no fading. After the second week of using the O.S.T. Vitamin C20 Serum, I noticed they had faded dramatically, and by day 28, they were almost gone. My overall complexion also looked visibly brighter after about a week of use, and my overall skin texture appears smoother now than it did a month ago, especially in my nose area. I’m fortunate not to have very large pores or any blackheads, so I am unable to comment on whether this serum helps with either of those issues.
In spite of the tingling sensation I experience when applying this serum, the O.S.T. Vitamin C20 Serum did not cause me any visible skin irritation aside from some very mild peeling during my first couple of weeks using this product (the ascorbic acid is exfoliating, after all). When the peeling did occur, it happened at the end of the day, which leads to be believe I probably wouldn’t have noticed it as much had I been using this product in the evening as directed – the dead skin would have washed away with my morning facial cleanse.
I’ve been using this serum for going on 33 days now, and definitely plan to finish the bottle. I love the results I’ve been getting from it, and I’m looking forward to seeing my hyperpigmentation spots completely disappear. I would definitely consider purchasing the O.S.T. Original Pure Vitamin C20 Serum again, especially since it’s priced affordably at $25 retail. I will probably experiment with some other serums first though, now that I’m back on the Vitamin C train!
- Highly effective against acne marks/post-inflammatory hyperpigmentation (PIH)
- Improves skin texture
- Effectively brightens skin tone
- Packaged in a dark bottle to delay product oxidation
- Smells like fresh oranges
- Contains a high amount of Vitamin C
- Tingles a bit during application
- Contains a couple of questionable ingredients
- The Vitamin C source is just okay for topical application
Skin & Tonics Rating:
Performance: 5/5 – Very effectively fades acne marks, improves skin texture, and brightens as promised
Quality: 3/5 – The packaging is okay, but would be better as an airless pump. Overall ingredient list could use some improvement.
Value: 5/5 – Very well priced for such a highly effective product
Where to buy
This article features a press sample that was sent to me for my unbiased consideration. Any opinion expressed is 100% my own. For more information about my review policies, see my full disclosure.
This post contains affiliate links. Shopping these links helps support this site. Full disclosure.