C20 vs C21.5 aka The Battle of the Vitamin C Serums

7:37 PM Moi Sanom 0 Comments

C20 vs C21.5 aka The Battle of the Vitamin C Serums

If I would have to guess which question I have been asked the most when it comes to Asian skincare it is probably how C20 and C21.5 compare to each other. C20, formerly known as OST, is an incredibly popular Vitamin C serum. The reason why it is so popular is because besides being very affordable it is really fantastic stuff. I really love it and you can see my near miraculous results and why I love it here.
It is one of those few products that actually visibly changed my skin for the better and that in quite a short amount of time. Funnily enough I didn’t expect any fast results at all when I started using it way back when. After all I was using the Vitamin C more for prevention than anything else.
You see Vitamin C is great at lightening pigmentation spots and post inflammatory hyperpigmentation (PIH) but also at boosting collagen production in the skin. The thing is that lightening pigmentation and boosting collagen is something that can take months to happen. So when C20 more or less obliterated my forehead lines I was more than surprised. 
I still don’t know why or how this stuff gets rid of my wrinkles so well but I am too happy to question it.

c20 before and after
This photo is from the original C20 review

The other immediate side effect that is reported by most users is the wonderful glow it can impart. For me the glow appears a few days to a week after use. It is hard to describe but when you see the glow you know what I mean!

The thing is that many people complained about C20 being a tad sticky despite its great results. I am not one of those people since hardly anything is sticky on my spongey skin but I know plenty of people who were not fond of that.
So one day C21.5 appeared, a new and improved version of C20. This was touted to be more effective and less sticky. 

C20 vs C21.5 aka The Battle of the Vitamin C Serums dropper

How do I use these Vitamin C serums?

From what I have read the most common way to use a Vitamin C serum is in the mornings. The reasoning being that since it is an antioxidant, it can help with the sun damage that can occur during the day.
Some people like using it at night because they like a shorter routine in the mornings when getting ready.
There is two camps on when you should use it in your routine. On clean skin after washing your face or after a low ph toner. If you use a low ph cleanser it is fine to use the serum on clean skin, but some people think it is better to use it after a low ph toner if you previously washed your face with a cleanser that has a ph of 6 or higher.

Then there is the waiting time. Since Vitamin C serums are PH dependent products and they need a low ph to give you all its benefits, it is advised to wait anywhere between 10 to 20 minutes before applying another product.

The way to use a Vitamin C serum, is just like all other skincare, quite personal. Some people do it this way, some do it the other way. I personally do all of the above. I have used the serum on clean skin or after a low ph toner. I have used it only mornings, only nights and both. And since I never really look at a watch I have probably have had any waiting time from 5 minutes to two hours (when I forgot to apply the rest of my routine). I have tried all the different methods to see what works better for me and in the end I saw good results with each so I ended up just doing whatever felt most comfy at the time. I will leave some links on the bottom for those of you who are more interested in the details of how and why Vit C works and other science stuff.

C20 vs C21.5 aka The Battle of the Vitamin C Serums swatch

So what is the difference between the two?

Will, let’s start with the similarities first.

Both serums are wonderful!
They are both equally effective. I can not speak for the collagen boosting action since there is no way I can measure that, but both serums give me a wonderful glow, make my fine lines practically disappear and lighten PIH. I have used about 4 bottles of C20 and 3 of C21.5 including some time of using one on half a face and the other on the rest of the face. I could not see any visible difference between the two on my skin.

The packaging and smell are identical so if you dislike one than you will likely dislike the other. I am personally fond of the packaging. Dropper bottles are my favourite after airless pump bottles and since the smell is not so strong and disappears fast I have no complaints about either. 

So are they different at all?

The biggest difference is in the texture and finish.

C21.5 is noticeably more liquid than C20. Some people prefer that but I'm not fond of it. The reason being that I lose quite a bit of product through the crack of my fingers. Also I prefer thicker textures since they are more comfortable to apply to my skin for me. 

C20 vs C21.5 aka The Battle of the Vitamin C Serums gif

The other difference is that people say that C21.5 is significantly less sticky than the original.
The thing is that since I didn't find C20 sticky I dont really notice a big difference in the updated version. I have asked a few people if they had issues with the stickiness of C20, and even though they confirmed that it was indeed a little sticky they said it did not make them want to stop using the product and that it disappear once the rest of the routine was applied on top. Those same people also commented that C21.5 is indeed less sticky but also leaves a tiny bit on the skin when applied. To me it really is a negligible feeling since both serums absorb quite fast and as mentioned before it is not noticeable when you apply more skincare on top. 

So which one should I get?

Well, it really is up to you. It is a very individual and subjective decision. I have heard everything from “they are the same” to “one is way better than the other”. I think the best way is to simply get the original, try it out and then test C21.5. You can then judge properly which one you prefer for yourself.
Both products are really excellent so in the end whatever you are most comfortable with works best.

Have you used one of these or both? If so what did you think and did you have a favourite?

Purchased at Wishtrend: C20, C21.5

Sources: 1, 2, 3, 4

Here is a referral code " 021617712" for those of you who are interested and don’t have a Wishtrend account yet. It gives you a 5$ discount upon signing up. Yay for savings!

Disclaimer: This post contains affiliate links and codes. That fact does not alter my review or opinion in any matter For more information read my Disclaimer page.