asian cosmetics beauty PR Sample review Wishtrend

Review: OST C20 Pure Vitamin C21.5 Advanced Serum

18. March 2015

You may know that one of my favourite products from Wishtrend is the OST Original Pure Vitamin C20 Serum. I reviewed it previously, but I didn’t have any before and after pictures. Nevertheless, I was really impressed how the serum changed my skin and made it so much better in various aspects. When I saw that there was a new version of this I was most excited to try this new OST C20 Pure Vitamin C21.5 Advanced Serum. And, as you might guess I had high expectations for this serum. Could it hold up to them?

OST C20 Pure Vitamin C21.5 Advanced Serum

The brand OST or C20 is best known for the popular OST Original Pure Vitamin C20 Serum in it’s signature orange packaging and the brown bottle. This serum is highly effective in terms of using the peeling ability of ascorbic acid in order to improve the skin condition. Despite being effective, it had some minor cons, for example it was very sticky, it was too aggresive for people with sensitive skin and it contained some artificial ingredients. The new OST C20 Pure Vitamin C21.5 Advanced Serum has a completelly different ingredient list and as the name says, the amount of vitamin C serum has been increased, too. The original serum contained 20 % of Vitamin C whereas in the new formula you will have 21.5 %. Vitamin C is an antioxidant and thus can prevent our skin from aging too early. The content of Vitamin C in both serums compared to other vitamin C containing products is rather high. It contains 20 % (21.5 %) 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.

OST C20 Pure Vitamin C21.5 Advanced Serum

As with the previous serum the cardboard box comes with a lot of description in Korean and in English. It is very detailled in how to use it and what precautions to take. The new serum has even more details in English, than the previous packaging. The ingredient list of the new formula is very short. You can look them up on COSDNA and you’ll discover that the ingredients are safe to use and that there is no artificial ingredient either. The ingredients of the old serum were safe to use, too, but the list of substances is much longer as you can look up >>here<<. Since both products contain Vitamin C they have to be stored in a cool place. They also do have to be protected from sunlight, in order to prevent the vitamin C from oxidizing. When I received the product the manufacturing date was really fresh, which is important for vitamin c products, too, because they have a short shelf life. Usually, I would recommend you to use it up as quickly as possible after opening.

OST C20 Pure Vitamin C21.5 Advanced Serum

You will find more information and detailled description about the serum on Wishtrend, too. The signature orange cardboard box contains a brown glass bottle and a separately packed dropper. You can simply exchange the lid of the bottle with the dropper after opening.

OST C20 Pure Vitamin C21.5 Advanced Serum

The dropper makes it very easy to take out the watery and runny product. The OST C20 Pure Vitamin C21.5 Advanced Serum has a clear color, which is also a sign that the vitamin C serum is fresh. If it turns yellow the vitamin in the bottle has started to oxidize. The scent of the product reminds me a bit of oranges, but with a different scent combined, which I cannot figure out. The scent is not strong and doesn’t linger on the skin, so it doesn’t matter anyways.

OST C20 Pure Vitamin C21.5 Advanced Serum

I’ve been using the OST C20 Pure Vitamin C21.5 Advanced Serum for 3 weeks now in the evening and on most days in the morning, too. When used during daytime keep in mind to use a sunblock, too! Below you can see how the serum effected my skin.

OST C20 Pure Vitamin C21.5 Advanced Serum OST C20 Pure Vitamin C21.5 Advanced Serum

I had some redness, when I started to use the serum. After 3 weeks the pictures show that the redness has decreased and I could feel that my skin is smoothened. Apart from this I didn’t experience any changes in my skin structure. I used this serum in combination with the Klairs Moisture Rescue Kit I reviewed previously. I used it after the Klairs Supple Preparation Facial Toner and the Klairs Rich Moist Soothing Serum and before putting the Klairs Rich Moist Soothing Cream. Sometimes I mixed the cream with a few drops of the vitamin C serum instead. The Klairs products may have contributed in reducing redness, too. The OST C20 Pure Vitamin C21.5 Advanced Serum is definitively less sticky than the old formula, but it is still a bit sticky, which is why I still like it better mixed with some other product.

OST C20 Pure Vitamin C21.5 Advanced Serum

Did the new OST C20 Pure Vitamin C21.5 Advanced Serum fulfill my expectations? I’m not sure. Somehow I have the feeling that the old formula was more effective. I remember with the old formula, that I felt a stinging experience the first times I used it. I didn’t have any feeling like this for the new formula. Maybe, this new formula is better suited to sensitive skintypes than the old one. I could observe a decreased redness in my face, but I cannot assure that it is only due to the new vitamin C serum, but it will be a combination of my skincare routine as a whole. Maybe if I repurchased this serum I would go for the old version, just because I had the feeling it worked better for me (and to confirm my observation). I can recommend you to try this new formula of the C20 if you were unhappy with the previous ingredients. This formula is almost completely different and doesn’t contains any parabens or other artificial ingredients. It doesn’t contain alcohol either. The old formula does have some cons, like the extreme stickiness and the ingredients, but I would not claim that the new formula shows better results, even with a higher concentration of vitamin C. Both serum, the old and the new version can be purchased at Wishtrend. The old OST 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 OST C20 Pure Vitamin C21.5 Advanced Serum retails for 24.99 US$. Both bottles contain 30 ml. I made a post about the promotions from Wishtrend for March >>here<<. Also, keep in mind their friend-referral program: You can receive a 5 Us$ 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.


I shared this post with the Asian Beauty Blog Link Party! Feel free to check out the beautiful reviews presented in their threads:


Just as a short reminder: All products mentioned and reviewed on this blog are of my personal opinions. This product here was sent to me for reviewing purpose by, which doesn’t influence me in providing my honest opinion on the products.

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  • Evelyn 18. March 2015 at 16:43

    Thank you! This is now on my wishlist to fight pimples haha :D

    • Frl. Schnee 19. March 2015 at 21:24

      A lot of people are curious for this serum. As I said, depending how sensitive your skin is, the old one is working the same. That was my impression :) Looking forward to read your review :)

  • Sam+Murakami 18. March 2015 at 21:22

    Oh dein Rating System am ende is ja mal voll süß :D Ich hab ja auch ne Review über das alte OST gemacht und fand das immer ausreichend – ich persönlich seh nicht ein für 1.5% mehr Vitamin C das doppelte oder so zu zahlen ^^” (Zumal ich auch immer noch keine verlässlichen Quellen gefunden habe ob die Haut mehr als 20% überhaupt sinnvoll verarbeiten kann oder nicht) Kannst du was von Klairs empfehlen? Ich wollt die Sachen immer mal ausprobieren, konnte aber als ich in Korea war bei Wishtrend nichts bestellen -.-
    Liebe Grüße!

    • Frl. Schnee 19. March 2015 at 21:22

      Danke schön :D ♥ Ich mochte das alte Serum auch sehr gerne und ich denke, dass ich das auch wieder kaufen werde, wenn ich vor der Wahl stehe. Ich bin mir sicher, dass die Haut nicht soviel Vitamin C aufnehmen kann. So hohe prozentuale Werte wirken ja hauptsächlich wegen ihrem Peeling Effekt und nicht weil das Vitamin C aufgenommen wird. Und diese 1.5 % machen sicherlich keinen Unterschied.
      Ich mag von Klairs das Reinigungsöl und den Toner und würde auch beide jederzeit neu kaufen!

  • Claudia 18. March 2015 at 23:00

    Thank you so much for this review? Is it absolutely crucial to keep this product in a fridge? It is sort of inconvenient for me, because the only fridge in my house is very far from my kitchen. Is it ok to just leave it in a dark place?

    • Frl. Schnee 19. March 2015 at 21:19

      If your bathroom is cool in temperature and you will use it up quickly anyways it is no problem, just be careful not to have it in warm environment.

  • Kim 19. March 2015 at 2:28

    I think I am going to get this serum with my wish trend voucher! It looks so good! Your skins already perfect anyway :P. I have lots of scars now so hopefully it works on them! Thanks for reviewing! The new one does sound better for its decreased stickiness.

    • Frl. Schnee 19. March 2015 at 21:18

      Oh, my skin is far from perfect :D And I start to see that I’m getting “old”, haha…but honestly, it is surprising to see how your skin changes during age :D I hope the serum works for you! I saw images for the previous formula of this serum which should huge differences in before and after.

  • Sakuranko 20. March 2015 at 2:46

    I´ve seen this serum several times before but never ends on my wislist I´m not sure why. Thanks for this review

    • Frl. Schnee 2. April 2015 at 17:53

      It has been reviewed by so many people. Nevertheless, I’m happy you stopped by reading ♥

  • Tammy 20. March 2015 at 20:37

    It’s interesting that you think it’s less effective than the original version. I like the original version despite its stickiness and my skin isn’t especially sensitive. Hmm.. judging by your review I think I would prefer the old version but do you know if they will stop making the C20? Or will they have both on the market?

    • Frl. Schnee 2. April 2015 at 17:56

      I think they will keep both for now. But not sure either. Since the ingredient list of the two products is quite different it maybe that my skin was simply happier with one of the old ingredients…but I do not have any other explanation why I like the old formula better.

  • Rebecca+B.+Bird 20. March 2015 at 22:40

    I think the fact that this version is less sticky than C20 will be a major selling point for many people – that is the complaint I hear most often about C20. I do want to try C21.5 – $24.99 is still pretty affordable compared to other options!

    • Frl. Schnee 2. April 2015 at 17:57

      That’s true. More people will buy it if they hear it is less sticky…and you’re right, it is still affordable compared to other vitamin C serums.

  • Arcy 6. May 2015 at 11:41

    I like your honest review. It seems that every blog I read regardless of product, it is always positive and have nothing bad to say about the products they are blogging about.

    With the original formula (sticky), did you find that when applying your moisturizer it clumped (i.e. serum and cream bonding to seem as if your skin was peeling)?

    • Frl. Schnee 20. May 2015 at 8:20

      Sorry for the late reply, I’m a bit behind answering comments atm. No, it didn’t clump. I used it on its own and mixed with cream, altough some people suggest to use it as first step and wait for at least 15 minutes to gain more benefits from the vitamin C. I tried that version, too, but I didn’t see any differences in the effectiveness than with my previous method.

  • Fiona K 19. May 2015 at 21:33

    I am interested to read your reviews, but I am concerned that Asian products will have been produced using animal testing. Do you have any information on whether the companies whose products you try Still test on animals or not?

    • Frl. Schnee 20. May 2015 at 8:23

      Some brands specifically state that they don’t test on animal, for example Innisfree, Klairs or COSRX. COSRX is also the brand behind C20 vitamin C serum or Ciracle. I think if you check out the official pages of the brand you are interested you will find information on this concern. I personally have the feeling that the trend goes towards natural and animal friendly cosmetics also in asia.

  • Jinyoung 16. June 2015 at 20:08

    I’ve been eyeing this product for quite some time now! But whenever there’s a new formula, I’m a bit wary as to which one might be better because it sometimes seems like there might not be much of a difference.

    So, you wrote that the texture for the 21.5 is less stickier than the 20. Does the stickiness make it hard to apply the product onto the skin or leave a residue?

    • Frl. Schnee 16. June 2015 at 20:35

      There is quite a huge difference between the two formulas. Actually some say it could be called a different product. The old version contains niacinamide for example and vitamin E. About the stickiness of the old version: it simply feels sticky n the face and if you apply a second product later above it will still feel sticky. This feeling is less, when the product is mixed with another cream before. It is not harder to apply because of the stickiness though.

  • [email protected] 23. April 2016 at 8:16

    At the moment, after a year of using this product, which one do u recommend? the older version or the upgeaded version?

    I am having dillema which one to get…:(

    • Frl. Schnee 23. April 2016 at 13:40

      It depends on your skin and how sensitive you usually react to skincare products. If you have sensitive skin I would recommend you the new version.

  • Min 23. April 2016 at 13:58

    Ahhh! Good review by the way :)
    I have ordered the older version because it’s really cheap now with free shipping . Only $14.99

  • Michiko 20. June 2016 at 11:15

    Hi :)
    Does the older version contain parabens and artificial ingredients?

  • serendipitousjoann 8. August 2016 at 1:38

    I’ve wanted to try this serum for ages. It seems to have become a staple for a lot of people.
    I think you sold me on 1. good for sensitive skin and 2. not sticky. I think I’ll try this out once I’m finished my other serums!

  • Sophie 9. August 2016 at 18:01

    I love that this doesn’t include alcohol, though the oxidisation is always something that makes me reluctant to try it out.

    Sophie | MapleTreeBlog

  • Lilian 26. September 2016 at 18:47

    Wunderbur, ich benutze das serum zu und Ich Rückkauf das serum. Danke aus Indonesien,

  • Sharmila 4. March 2018 at 18:28

    Hi ! Is it safe to use this serum during pregnancy ?

    • Frl. Schnee 20. March 2018 at 22:34

      Hello Sharmila, actually I do not know what the criteria are for pregnancy savety. I would recommend you to contact Wishtrend customer service.

  • Sharmila 21. March 2018 at 11:46

    Hi ! Thanks for ur reply. Sadly I did contact the Wishtrend Team and they couldn’t give a definite answer and asked to check with a dermatologist. It’s so unfortunate that many Skincare brands are not confident about their products when it comes to pregnancy.