Review: O.S.T Original Pure Vitamin C20 Serum

EDIT: A new version of the  O.S.T Original Pure Vitamin C20 Serum has been released, which is called C21.1 Advanced Serum. If you have sensitive skin I can recommend you to check out the review on the new formula >>here<<.

A couple of month ago I took part in one of Wishtrend’s giveaways and I was very lucky to be chosen as one of the winners. Around two weeks later I got a package from Wishtrend containing the popular O.S.T. Original Pure Vitamin C20 Serum. I’ve read a couple of reviews for this serum before and it did seem to work greatly on most of the reviewers, so I was especially curious for the effects.

O.S.T Original Pure Vitamin C20 Serum

The brand O.S.T or C20 is best known for exactly this serum reviewed here. O.S.T or C20 belongs to the same manufacturer as COSRX and Ciracle and is a Korean brand. The signature packaging of the O.S.T Original Pure Vitamin C20 Serum is the orange cardboard box containing a brown glass bottle with an orange label. Many people will ask themselves why to use a vitamin C serum in their skincare routine? Usually, Vitamin C serums help to keep your skin nourished. Vitamin C can help brighten your skin, it can act as chemical peeling when used in a high concentration and it has anti-aging properties. Sounds promising!

The O.S.T Original Pure Vitamin C20 Serum  has a volume of 30 ml and a shelf-life of 12 months after opening, although, since it is a vitamin C serum which oxidizes by time, you should use it up as quickly as possible. The cardboard box shows the detailed Korean description of the packaging. You can find English description on Wishtrend.
O.S.T Original Pure Vitamin C20 Serum Ingredients of the O.S.T Original Pure Vitamin C20 Serum are:
Water, Ascorbic Acid, Ethanol, Sodium Lactate, Butylene Glycol, Glucose, Camellia Sinensis Leaf Extract, Rosa Davurica Bud Extract, Carthamus Tinctorius Flower Extract, PEG-60 Hydrogenated Castor Oil. Sodium Hyaluronate, Bis-PEG-18 Methyl Ether 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

O.S.T Original Pure Vitamin C20 Serum

According to COSDNA the ingredients of this vitamin C serum are safe to use. There are some minor irritants though. Apart from vitamin C, the key ingredient, the O.S.T Original Pure Vitamin C20 Serum contains a mostly different moisturizers, some plant extracts as antioxidants, but also alcohol (Ethanol). Methylparaben is also listed in the ingredients. Sodium lactate, hyaluronic acid and niacinamide are some of the positive ingredients here, acting as moisturizer and brightener. Vitamin C is an antioxidant and thus can prevent our skin from aging early. The content of Vitamin C in this serum is very high compared to other vitamin C serum. It contains 20 % vitamin C. You have to know that a high concentration of Vitamin C doesn’t mean automatically that it is more effective concerning anti-aging. Normally, a high concentration of Vitamin C aims at a visible effect, because it tends to operate as a peeling by loosening dead and old cells. This is not a bad effect and stimulates the skin to regenerate itself, but keep in mind that it won’t affect the inner cell layers of your skin which have to be aimed if you really want an anti-aging effect.

The orange color of the packaging may be simple, but it reminds people of orange fruits, especially oranges, which makes them think about vitamin C automatically. The bottle inside comes with a sealed cap and a separately packed pipette. The pipette is very useful for the application of the serum and makes it possible to apply the serum carefully. Since vitamin C can oxidize the brown bottle is a good choice to prevent this, but you are even more safe if you store it additionally in the fridge, because warm/high temperatures can degrade the vitamin C as well.
Also make sure to close the cap of the bottle always tightly! As you can see in the image above, the color of the serum is a very light yellow. The color becomes more pigmented the longer you keep the serum, so it is best to use it as soon as possible, once the bottle is opened. A strong yellow color only means your vitamin C serum has oxidized!
As to the structure of the serum: it is a bit less fluid than water, similar to oil and has a similar thick consistency. When applied on the skin it leaves the skin with stickiness. I had no problems with the stickiness as long as I applied it only before sleeping. During daytime I didn’t want to have the sticky feeling. Finally, I started mixing 2-3 drops of the serum with my toner or moisturizer in the morning, which worked great and was much less sticky than putting it on your skin alone. The scent reminds me a bit of oranges. So, what effects did this serum have on my skin? I tested it for around 2 months now and it does some nice work on the skin: my skin feels more even and smooth and appears cleaner. I didn’t see a whitening effect or any effects on my black-/whiteheads (but I really don’t have many of them to begin with…). It seems the peeling effect by the vitamin C works really nice and the skin regenerates itself a bit, resulting in the nice feeling of my skin which I had. Since I liked the effect of it I can recommend you to try O.S.T Original Pure Vitamin C20 Serum by yourself. Perhaps it improves your skin, too and/or even helps with the other skin problems. One negative part I recognized was, that the serum stings the first few minutes after application. After a while this effect is not noticeable anymore though. If you tend to have dry skin like me, this serum can be a bit drying, but you can either mix the serum with a moisturizer or apply moisturizer afterwards.
I really like the O.S.T Original Pure Vitamin C20 Serum! It is affordable compared to other concentrated vitamin C serums and it is effective in terms of smoothing your face and making it look healthier. EDIT, since I can know compare this Vitamin C serum to the reformulated O.S.T C20 Pure Vitamin C21.5 Advanced Serum: The O.S.T Original Pure Vitamin C20 Serum is much more intense than the O.S.T C20 Pure Vitamin C21.5 Advanced Serum. On the other hand the C21.5 doesn’t contain any parabens or other artificial ingredients. It doesn’t contain alcohol either. Also, it is not as sticky and doesn’t sting as much as the C20. Nevertheless, I had the feeling that the C20 was more effective on my skin. I had more visible results on my skin. Which of the two is the better serum for your skin I cannot tell, but I can recommend you to try rather the C21.1 if your skin is very sensitive. Go for the cheaper C20 if you have quite normal skin. Both serum, the old and the new version can be purchased at Wishtrend. The old O.S.T Original Pure Vitamin C20 comes with free shipping and retails for 14.99 US$ at the moment, which is really affordable for a vitamin C serum. The new O.S.T C20 Pure Vitamin C21.5 Advanced Serum retails for 24.99 US$. Both bottles contain 30 ml. Check out my blog for the monthly coupon codes for your shopping experience at Wishtrend. Also, keep in mind their friend-referral program: You can receive a 5 Us$ referral coupon if you use my invitation code 17939205 upon registration and you’ll receive this voucher immediately. There will be a specific field in your registration form called “friends invitation program” where you can put the code mentioned above. This way new customers can safe 5 US$ which is a great possibility to safe some money.

42 thoughts on “Review: O.S.T Original Pure Vitamin C20 Serum”

    1. I didn’t have any problems during the time that I used it, but I have to say that Germany is not a country were the sun is permanently shining (especially not now) It may be that it reacts in another way if your skin is exposed a lot to sun, but that I cannot say. Also, I read a lot of reviews on this serum before I owned it by myself and all were positive, and if they were neutral they didn’t mention anything about photosensitivety…

    1. Too bad this didn’t work for you. Actually it is strange that you had an increase of oil while using it, since I had the feeling it was on the drying side…Thanks for commenting and reading ♥

  1. Wow I’ve read so many good review about this product, I really want to try one hopefully. Well since the Vitamin C is easy to be damaged by heat and sun, I think the best time to use this serum is night time only

  2. Hi hun,

    Someone might have let you know already, but when I go to your blog, I get a Malware warning from Google, encouraging me to turn back, because “Content from, a known malware distributor, has been inserted into this web page.”.

  3. I’ve heard so much about this product! I’m hoping to save up for it since it helps heal skin. *A*
    I’ll be sure to expect stinging and apply moisturizer since I have sensitive skin. :>
    Thank you for the review! <3
    Please check out my blog if you have the time! ;v;

    ☆ gin ★

  4. Since this serum has exfoliating properties, would you still use other exfoliating products 1-2 times weekly? I just bought a chemical exfoliator and am hesitating to purchase this because I’m afraid of over-exfoliating my face.

    1. If it is only a chemical exfoliator you use 1-2 times weekly I think you could try the OST Vitamin serum nevertheless. I would reduce your chemical exfoliator first to once a week and if your skin doesn’t react negatively, start using it twice a week like before. I use another vitamin c serum for reviewing purpose at the moment and I still use an AHA peeling 1-2 times a week and it doesn’t effect negatively, but my skin is not very sensitive either.

        1. I used it every night, but I didn’t use it daytimes, because it feels a bit sticky. If you mix it with your night cream it’s ok though. But don’t mix with niacinamide containing cream.It will oxidise the vitamin C.

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