OST Original Pure Vitamin C20 Serum Review

November 13, 2015

Hello everyone! This post will my review of OST's Original Pure Vitamin C20 Serum!

If you watch WishTrend's videos on YouTube or have been following Korean skincare trends, you've probably already heard of OST's C20 Serum. 

I've always wanted to try it but whenever it was on sale on Hermo.my, it always sold out before I could get myself a bottle. Hermo.my recently had a fan favourite sale where they had a sale for their top selling products and I managed to get myself a bottle! ^^ I also bought Tony Moly's Tomatox Magic Whitening Massage Pack which I shall also be reviewing soon.

On with the review!

*Disclaimer: This is my honest review and have not been paid to make this post*


This product is a serum that contains 20% Vitamin, which is quite a high percentage. I first found out about this from WishTrend and decided to do some research on it. A lot of bloggers have found that it gives very good results. A lot of people have written rave reviews about it because of its brightening, refining and balancing properties. 

On the back of the box it says: "C20 vitamin serum delivers a multitude of complexion benefits for beautifully healthy skin. Pure vitamin C refines, brightens and balances skin tone for a radiant appearance.

Something that has caused some misunderstanding is that this product rebranded and changed the product's name.

And because of its popularity, OST released an upgraded version called the Pure Vitamin C 21.5 Advanced Serum. This is currently believed to have the highest percentage of vitamin C in a product!

If you're wondering, why so much hype around Vitamin C? Well Vitamin C skin benefits are largely attributed to its benefits in supporting healthy collagen. Vitamin C provides antioxidant protection and when incorporated into your daily skincare routine it can provide a range of benefits such as:

- Reducing the appearance of sun damage
- Helps boost healthy collages production, leading firmer skin!
- Reduce inflammation and irritation
- Fades post breakout red marks
- Increase the effectiveness of sunscreen and boosts skin's defense against UV exposure

I've tried It's Skin's VC Effector (click here to see review) and I find vitamin C a great way to fade acne scars!

I've also tried the purest form of vitamin C I could find: Lemons. Lemons worked great at lightening my skin, but it can be painful for the skin, especially if you have acne. Using raw lemons are a great way to brighten skin, but remember that it is raw and unpurified. I also find the whole process of using lemons everyday a bit tiring. That's why I was so excited to try this serum out!


I bought mine on Hermo.my on sale at RM79.20 (including GST). The original price is RM99!

The serum (21.5) is also available on WishTrend.com and costs USD24.99. C20 is also available but if it were up to me, I would buy the 21.5. The more vitamin C, the better!


This product comes packaged in a box and the bottle with the serum comes like most 30ml serums, the only difference is that the dropper is packaged separately from the bottle.

The serum bottle is packaged with a flat screw cap sealed in plastic. The dropper comes packaged in a separate plastic.

The bottle comes sealed:

And as I opened it, a little bit of smoke actually came out! I closed it back because I wanted to take a picture of the smoke but when I opened the bottle it was gone. I think the smoke was something to kind of preserve the vitamin C from oxidizing (I THINK).



This serum is light yellow in colour, but at the back of the box it says that browning of the liquid is a natural phenomenon of highly concentrated vitamin C. The serum darkens as time progresses due to oxidation of vitamin C, much like lemons and apples become brown once exposed to the air. Do  not expose the bottle to sunlight and keep it in a cool and dry place.

I've read some reviews saying that keeping it in a room will turn the serum brown at about 3-4 months, whereas keeping it in a refrigerator keeps it fresher and the same colour even after 6 months of storage.

I didn't really want to keep it in the fridge because I found it a bit unsanitary to do so. I mean, do I really want to keep my serum in my apartment's shared refrigerator? After thee months of using it and keeping it in my room, the serum has turned brown, but in terms of function I would say that its still the same.

This change in colour is natural and its caused by the oxidation of the vitamin C.

As for the texture, the serum runs quite well. The consistency is thinner than It's Skin's VC effector but thicker than the WH effector. There is a very slight sticky feeling after absorption.

The serum smells citrus-y but not as much as It's Skin's VC effector. It's Skin's VC effector reminded me of lemons and while this one also smells a bit like lemons, I was reminded of the smell of berries as well. After a while of using it, I sometimes get a slightly burned smell, which I believe to be because of open wounds (more about that below).


As this is a serum, I apply it after I apply my acne products and before my moisturizer. If you use more than one serum, you can use the rule of layering and apply this first as the consistency of this serum is quite light.

Cleanser - Toner - Essence/Lotion - Eye - Acne/Spot - Serum - Moisturizer

Although light, I do not recommend using this product in the morning or when going into the sun. This is due to the high concentration of vitamin C which cannot be exposed to direct sunlight. I use this mostly during the night.

When I apply this I use two methods:

1. Use the dropper to drop the serum directly onto your face and massage it onto your face with your fingers. I usually apply a drop each to my forehead, cheeks, chin and nose (total 5 drops, which is quite a lot)

2. Use the dropper to drop 3-4 drops onto your palm, rub your palms to warm up the serum and apply it to the face by gently patting it.

The reason why I alternate between these two methods is that no matter what skincare tutorial I watch, its either one of these methods. Both seem to have logic so I decided to alternate.

One thing I learned while using this in the long run is that if you have a pimple that burst, do not apply this serum on it. It will sting and burn that spot, but I have found that after this so called "burning" of open wounds, the spot will immediately have a scab the next morning and sometimes I could easily peel off these scabs and the pink raw skin would be unveiled. I DO NOT recommend this method, its just something I've observed.

Also, do not apply too much. I applied too much one night because I accidentally pressed the dropper and the excess vitamin c transferred from my face to my pillow, staining it. Its washable, but do you really wanna waste serum?


As I said, there is a slight tingling on pimple areas (even unpopped ones) and there is a definite stinging on open wounds, the sensation is kind of like burning the acne.

Aside from that, I have nothing else but positive feedback for this serum! I did feel that my skin was firmer, especially in my cheeks area and forehead area. It does a marvelous job of fading scars and dark marks quickly as well! Of course my skin isn't flawless now, but it has managed to fade a lot of acne scars. I also feel that my skin appears more radiant now. It has managed to somehow balance my skin tone and make it less patchy.


This has easily become one of my favourite products and I make it a habit to not skip this serum. If I had to compare it with Its' Skins' VC Effector, I'd say that my skin absorbed C20 better and faster than VC, C20 had slightly faster fading properties and it was more comfortable to have on my face as C20 isn't as thick as VC. 



Because of the results, I would definitely want to repurchase this, but because of the price, I am a bit held back. As a student, RM100-125 is a bit expensive for serum, especially when I can get two or three bottles of It's Skin serums for the price of one bottle of C20. It is an investment though, and it does go on promotion. Plus, in the end it is the effect that matters, so YES, I would definitely repurchase this!

Thanks for reading this review! If you're interested in reading more, click here! If you want to read my review on It's Skin's VC Effector serum, click here!

Thanks for reading!


  1. I'm glad I came across your review. It's pretty informative and digestible to read :)
    I have an acne prone/Combination at summertime and dry at winter type of skin. my skin started breaking out once I turned 19 -I'm 20 now- and ever since i payed so much attention to my skin and products that I consume internally or externally. I've been following the typical 5 steps Korean skincare routine (Cleansing- toning- serum- eye cream- Facial cream) for almost a year now and I've noticed a change -not a marvelous on- on my skin in terms of balancing the amount of oils and keeping in the moister. but I'm disparately looking for a solution for acne/acne scars issue :'( .. I've used those two serums Separately and yet couldn't find any significant results. my issue might be hormonal and requires a pro dermatologist. however, do you suggest i combine the VC & C20 serums in my skincare for an almost better results?

  2. You can buy it cheaper at shopee. I got my bottle for RM65 only, as i am also a student, the serum can be quite expensive to repurchase, but it's so good that i just have to repurchase.

  3. Bibliography - Paul, Steve. 2018. “Stinging Nettle Testosterone - Benefits, Dosage & Side Effects!” Testosteroneofficial.Com Ie. Testosterone Official. December 13. https://testosteroneofficial.com/research/stinging-nettle/


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