OST C 21.5 SERUM REVIEW | OST Pure Vitamin C 21.5 Advanced Serum

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OST C 21.5 SERUM REVIEW | OST Pure Vitamin C 21.5 Advanced Serum

This review contains affiliate links.
It is not a sponsored review and is my true and honest opinion and results of the product.

Serums are the new hot item in skincare and a must have in every morning and night time routine. We now find our selfs looking for serum and products that contain Vitamin C that will help even out our skin tone. Vitamin C serums are great for fading post acne scars, sun spots, pigmentation and even help to fight against acne.

Today I am going to share my review on the new formula of the OST Pure Vitamin C 21.5 Advanced Serum. The upgrade of the OST Pure Vitamin C 20 Serum. You can view my previous review of the old formula by clicking here.

Serums that contain high concentrates of vitamin C aren’t always the most pleasant to use. The number 1 issue being the texture of the serum being too sticky. Overly sticky serums block the absorption of additional layered skincare products, limiting their effects and overall be uncomfortable and unpleasant to use.

OST C 21.5 SERUM REVIEW | OST Pure Vitamin C 21.5 Advanced Serum

You can tell how sticky a serum may be by seeing how thick the consistency of it is. As shown above, the OST C 21.5  Serum travels at a medium rate down the surface of my skin. Just slow enough to give me enough time to click the shuttle button on my camera before the serum disappeared down my skin.

The second way to compare which product is more sticky is to apply any type of powder substance overtop of the applied serum.

In the above photo, I placed sugar over OST C 21.5 Serum. I used 3 drops of serum on the skin before hand. After shaking off the sugar, you can see almost all the sugar was easily removed from the skin where the OST C 21.5 Serum was applied.

Let’s test and see how the OST C 21.5 Serum effected my acne scars over the time span of 10 days of use.

OST C 21.5 SERUM REVIEW | OST Pure Vitamin C 21.5 Advanced Serum

The serum applied smoothly and absorbed quickly into the skin with a slight sticky texture that faded after 1 minute. When first applied, I felt a slight tingling and burning sensation. After a few seconds, the sensation went away. I then waiting 15 minutes before applying any additional product to make sure the serum was fully absorbing into my skin without being diluted.

Over the time span of 10 days, I did not experience any skin irritations. No hives, no itching, no burning and no redness. My skin actually improved very quickly in only 10 days of use. The redness in my cheeks improved, my pores appeared tighter and my acne scars started to heal very quickly!

I was very shocked at how quickly this serum worked for me in comparison to the old OST C 20 Vitamin C formula.

What makes me the happiest about this new formula, is the small amount of ingredients used. Making the OST C 21.5 Advanced Serum much less sticky and less irritating to anyone with sensitive skin.

OST C 21.5 SERUM REVIEW | OST Pure Vitamin C 21.5 Advanced Serum


Based on my personal results with the OST C 21.5 Advanced serum, I would choose the OST C 21.5 Serum over the old OST C 20 Serum as it did not cause me any irritations and provided my skin with the results I was hoping for out of an vitamin C Serum.

The new OST Vitamin C 21.5 Advanced Serum is something I highly recommend to include in anyones skincare routine who is looking for a Vitamin C Serum that is less likely to cause irritation and will improve the appearance of post acne scars and other skin pigmentation concerns.


OST Pure Vitamin C 21.5 Advanced Serum

Check out the new and improved OST Pure Vitamin C 21.5 Advanced Serum at Wishtrend

 :: Get It Here ::

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OST C 21.5 SERUM REVIEW | OST Pure Vitamin C 21.5 Advanced Serum






OST C 21.5 SERUM REVIEW | OST Pure Vitamin C 21.5 Advanced Serum

Bronwyn Papineau (BiiBiiBeauty)
Hi! I am Bronwyn Papineau AKA BiiBiiBeauty & BiiBiiBap. Welcome to my area of the internet :3 I blog about my life and review the things I love while I travel. I am a beauty blogger & youtuber from Toronto Ontario Canada who lived in Seoul South Korea for 2 Years, Tokyo Japan for 1 and now Melbourne Australia. So, come with me on my beauty journey!

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  • Frl. Schnee February 12, 2015 6:44 pm

    The before and after effect really shows some improvement. I’m happy they changed the formula to a less sticky one, because with the old OST20 this was my main problem. I had to mix it with moisturizer so it was at least a bit less sticky.

    • biibiibeauty February 13, 2015 1:30 am

      I was shocked by the improvements. I didn’t notice how fast it worked until I compared the photos. I am super happy with this serum! 🙂

  • Jolanda February 16, 2015 5:50 pm

    Thank you so much for this in depth review. I’ve had my eye on this serum for a wee while now and I will definitely purchase it now I know it works so well! Thanks again! xx

    • biibiibeauty February 17, 2015 2:04 am

      I’m happy the review was helpful to you! 🙂

  • BeautySushi February 16, 2015 8:57 pm

    Whoa!!! The difference between before and after really shows!
    This product really seems worth a try! I don’t have acne but my friend does, I’ll recommend it to her >.

    • biibiibeauty February 17, 2015 2:03 am

      I know right! I couldn’t believe it either! 🙂

  • Sora July 16, 2015 7:52 pm

    One question, did you use it all over your face? because in various sites it says it shouldn’t be used all over, but rather as a spot treatment for PIH, so I don’t know which I should buy.

    • biibiibeauty July 17, 2015 1:40 am

      I apply is all over my face. But I avoid the eye area. If your have PIH, then you can use an additional drop and apply it to targeted areas that need extra help.

  • Lia August 12, 2015 6:25 pm

    For reducing acne scars, brightening skin, and evening over skin tone and complexion, would you recommend OST C 21.5 SERUM or the Klairs Freshly Juiced Vitamin Drop Serum?

    • biibiibeauty August 13, 2015 3:58 am

      Hi Lia,
      For fast results, C21.5 is the best choice. However take into consideration, with is 21.5% VS 5% vitamin C, it is prone to faster expiration and can cause skin sensitivity. If you have never sensitive skin, then Klairs would be best. If you skin is not very sensitive or is okay with Vitamin C products, then C21.5 is best 🙂 Klairs is more of a gentle brightening and mostly an anti-aging anti-oxidant product. While C21.5 is more for whitening and scar healing as well as anti-oxidant.

  • Lily September 23, 2015 2:27 am

    I have a really oily acne prone skin type! Can i use this? what other things would you recommend me. To clear my acne and for scars to fade away. Thanks

  • Lily September 24, 2015 1:55 am

    Thank you for your response. I forgot to mention this but i checked your skin routine video and was interested in few things that you mentioned.
    My skin is really oily so, would the products mentioned below be ok for my skin?
    1. Cosrx Bha Blackhead Power Liquid 100 Ml
    2. Cure Natural Aqua Gel 250ml
    3. Missha Time Revolution Night Repair Science Activator Ampoule SeRum

    Thank you once again:)

    • biibiibeauty September 24, 2015 2:47 am

      All the products are okay for oily skin types as well 🙂

  • aria September 27, 2015 2:26 am

    is this a morning serum or night serum?

    • biibiibeauty September 30, 2015 9:37 am

      Both. Just make sure you start using a sun cream when using vitamin c in your routine. Vitamin c make your skin more prone to sun damage all year round.

  • aria September 27, 2015 2:41 am

    i see that Missha Time Revolution Night Repair Science Activator Ampoule Serum can be used both day and night. Can you tell me whether the 21.5 serum is a day serum or night? And if you had to pick one serum from these two, which one would you pick?

    • biibiibeauty September 30, 2015 9:38 am

      Yes, you can use it day or night, just make sure you use a sun cream when you use this product in your routine as it has ingredients that make the skin more prone to sun damage. Use the 2 serums at different times. I use vit c during the day with sun cream and missha at night. If your looking to get rid of scars, use vit c. if your looking for an all around skin repair and anti aging serum, use missha.

  • Mary October 7, 2015 10:41 am

    Hi, I still have active acne and lots of acne scars, is the vit c suitable for me? Will it cause more breakouts initially?

    • biibiibeauty October 27, 2015 3:53 am

      Yes, it is a good product to help skin healing 🙂

  • Engelia soei November 5, 2015 1:51 am

    How often do you use the serum? Do you use it everyday?

  • tanzin November 25, 2015 1:13 pm

    hi can i use it with retinol A(isotretinoin) together or separately?????? is it effective for oily dark coloured asian skin??????

    • biibiibeauty November 25, 2015 6:02 pm

      Start by using them separately or patch testing them together. 🙂

  • Wendy January 9, 2016 8:19 am

    Thanks for the review-! I got mine in the mail about 3 days ago and started to use it every night. But today, i noticed some white stuff near the cap. It looked like mold to me but I read somewhere that it could be vitamin c crystallized. Should I be worried about this or is it fine to keep using it? Thank you in advance 🙂

    • biibiibeauty January 15, 2016 5:14 pm

      That is normal crystallization 🙂 This can occur around the cap and sometimes in the dropper.

  • Jessica January 24, 2016 6:24 am

    My skin it’s not extremely dry nor with a lot of acne. I do have small pores and blackheads. Can i still use it? I’m 20 years old. Is it good for fine lines?

  • David February 14, 2016 12:28 am

    Hi, can I use this vitamin C serum and mandelic acid together with salicylic products? What will happen? Thanks.

    • biibiibeauty March 9, 2016 9:48 pm

      Sure, just allow time for it to absorb before applying products overtop.

  • Patricia April 5, 2016 3:21 am

    Hi! big fan of yours from Toronto! I’m just wondering how do you use the serum? Reading from various online sources, some of them said you have to wait for 20 minutes after cleansing or apply it first before toner. So… I’m kind of confuse how to use this serum. What do you think it’s the right way?

    • biibiibeauty July 9, 2016 4:14 am

      You don’t have to wait that long. I never do and the results are the same as if i did. Just wait long enough for the serum to absorb 🙂 The choice of how long you wait is up to you.

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