REVIEW of OST Original C20 Vitamin C Serum+Benefits of Vitamin C+Klairs vs C20

Hello to our wonderful viewers once again. Today, we’re going to be adding a new part to our website, which is KBeauty! KBeauty, particularly its skincare, has been recieving praise from beauty experts and skincare-addicts all around the world. It’s inexpensive, effective, and uses new ingredients that are hard to find in the Western-skincare world. Plus, the packaging is adorable!


For the first KBeauty post, I’m going to give a review on the OST C20 Pure Vitamin C Serum. (One minus of kbeauty products are the ridiculously long names) But before we get to the review, I’m going to give a quick introduction to my skin type. Whoever said that all Koreans have naturally great skin, I think I’m here to prove you wrong. I have slightly sensitive, typical teenage skin, which is more combination than completely oily. I had a lot of acne in the forehead area, PIH(Post-Inflammitory Hyperpigmentation, aka acne scars), and I also wanted to brighten my skin a bit.


I had just learned of chemical exfoliators and the benefits of Vitamin C, and the C20 Serum seemed like the most popular choice. People seemed to be showering it with praise, so I picked up a bottle on for about $13 when it was on sale, with the regular price being $16.40, on amazon. The new, updated version is about $23, but for me there isn’t much of a difference in results.


Ingredients: Water, Ascorbic Acid, Ethanol, Sodium Lactate, Butylene Glycol, Glucose, Camellia Sinensis Leaf Extract, Rosa Davurica Bud Extract, Carthamus Tinctorius (Safflower) 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, Tocopheryl Acetate, Lecithin, Caprylic/Capric Triglyceride, Ubiquinone, Diisopropyl Adipate, Phenoxyethanol, Methylparaben. CosDNA analysis.

Water is a filler ingredient, so it’s a bit dissapointing that it’s at the top of the list. Ascorbic Acid is the from of Vitamin C being used, and the concentration is 20%, as the name suggests. Anyone allergic to alcohol or any of the essential oils shown below would want to use the upgraded C21.5 Serum, which has less harmful ingredients for a bit higher price.


How Care for C20: The one downside of the serum is how high-maitinence it is. It should be kept in the fridge, away from sunlight, and usually only lasts about 3 months before it oxidises. Once it turns orange, or oxidises, the serum is basically useless.


How to Use: After using a low-ph cleanser, or using a ph-adjusting toner, apply all over the face and wait for 15-20 minutes before putting anything else on. If you have any “first essences,” you’re going to ignore the “first” of the name and put it on after the 20 minutes is up.

Keep in mind, in order for chemical exfoliation of the vitamin C to work, your skin must be at a ph of 5.5 or lower. We may have a post on PH levels and how to create your skincare routine around it, but as for now, keep in mind that you need to use a cleanser that has a PH of 5.5 or lower, or you have to use a ph-adjusting toner. I use CosRX’s Good Morning Gel Cleanser, which I like and will probably do a review on later. As for ph-adjusting toners, I’ve heard that Mizon has a good one. However, you really should be using a 5.5 ph-level cleanser in the first place, if you don’t want to damage your skin’s lipid barrier.

Also, it’s best to use it only in the PM, since Vitamin C makes your skin photosensitive. And THE MOST IMPORTANT FACT is that you always, ALWAYS should wear sunscreen, but especially if you use a Vitamin C serum. If you don’t wear sunscreen, your skin will quickly rid of any benefits it could give you. This goes for any vitamin c serum.



If I were to pick one product that transformed my skin, I would probably pick this serum. I’ve ordered 3 bottles, and I don’t know what I would do without it. This is super effective on PIH, so anyone with acne scars, this is the one sole answer. My acne has also been under control. Whereas my forehead used to be a battle ground, now I usually only have one or two flare-ups every week. My skin has definetely brightened up a bit too. The only thing I would recommned is always using a moisturizer, since only putting on this serum would probably be too drying. It doesn’t do a ton for blackheads, so if blackheads are your main problem, I would advise looking elsewhere.


C20 vs Klairs:Which One?

C20 Serum
Klairs Vitamin Serum






I just wanted to add that another very popular vitamin C serum is the Klairs Freshly Juiced Vitamin Drop Serum. I used this one before I got the C20, in fear that the high concentration of Vitamin C in the C20 would irritate my skin. I have to say, in my personal experience, I found much better benefits from using the C20 serum. The Klairs was 15% less Vitamin C, so there was less benefits, but I also didn’t really like the texture of the Klairs. It was a very greasy feeling, so I hated wearing it in the morning. Some describe the C20 as having a tacky feeling and having it hard to have their foundation stick on, but it didn’t really affect me since I only put it on in the nighttime, and because I don’t usually put on makeup. If the texture is the problem, I’m pretty sure that the new C21.5 serum is made for those who feel that it’s too tacky. Those with extremely sensitive skin might want to opt for the Klairs.


Before and After Photos:

Although the after photos are much later, I acutally saw results after about a week, or maybe even less of using it.



As you can see, my forehead wasn’t a great sight, and it doesn’t feel nice knowing that you have the Civil War raging on your face. Here’s a photo I took after I used this serum and updated my old skin routine. I kid you not, I didn’t photoshop the photo. Such a drastic change, right?



Overall Rating: 4.5/5

The results that I got from the serum definetely were able to meet my expectations, and it’s done wonders for my skin. The only complaint that I have is the fact that the Vitamin C isn’t as good at keeping blackheads at bay, and the fact that it has a limited shelf life. Other than that, I love it. It’s cheap, effective, gave quick results, and it’s a multi-tasker. Anyone with troubled skin, or skin that needs a little brightening, this will be you next 필수템(Pil-soo taem), or must-have item.

error: Content is protected !!
%d bloggers like this: