Review | Paula's Choice Resist C15 Super Booster (plus comparison to OST C20) | Hello Pretty Bird! - A beauty and not-so-glamorous lifestyle blog

23 February, 2015

Review | Paula's Choice Resist C15 Super Booster (plus comparison to OST C20)

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I recently cracked open my second bottle of Paula's Choice Resist C15 Super Booster, so I thought it was about time I shared my thoughts. Major spoiler: I like it (as you may have guessed from the fact that I already repurchased it), but I still think the OST/C20 Vitamin C serum is better at providing quick-n-dirty results. There are several ways in which Paula's Choice C15 is superior though, so in addition to reviewing C15 in this post I'll also be doing a bit of comparison between the two so folks who haven't tried either can make an informed decision about which one to get.

Paula's Choice Resist C15 Super Booster vitamin c serum

Product description:
"Brown spots don't stand a chance. Add a few drops of this booster to your serum or moisturizer daily, or use it alone. It's the new anti-aging superhero."

Note: This is touted mainly as an anti-aging product, but Vitamin C products can also be effective at lightening post-acne hyperpigmentation. Personally I use it for a combination of anti-aging and acne-healing benefits.

US $48 for 20ml/0.67fl oz or US $20 $9 for a 3.5ml sample.


Water, Ascorbic Acid (vitamin C/antioxidant), Ethoxydiglycol (slip agent/penetration enhancer), PPG-26 Buteth-26 (emulsifier), PEG-40 Hydrogenated Castor Oil (thickener), Tocopherol (vitamin E/antioxidant), Ferulic Acid (antioxidant), Sodium Hyaluronate (skin-repairing ingredient), Acetyl Octapeptide-3 (cell-communicating ingredient), Glycerin (skin-repairing ingredient), Panthenol (skin conditioning agent), Sodium Metabisulfite (stabilizer/antioxidant), Triethanolamine (pH adjuster), Phenoxyethanol (preservative).

The pH level of this product is approximately 3.0. There are a couple of notable things about this formula: One, it is free of alcohol, and two, its use of Ferulic Acid, which has been shown in research to stabilize the formula of and increase photoprotection of the skin in C/E serums made with l-ascorbic acid (source).

Paula's Choice C15 comes in an opaque orange bottle with the dropper packaged separately from the serum, which is a very good idea for the sake of preservation. Most Vitamin C serums will start to oxidize quickly once opened and exposed to air, with an average shelf life of around 2-3 months. The Paula's Choice serum is a very light champagne-y color when first opened, and after a couple of weeks it will start to turn slightly yellow like this:

Paula's Choice Resist C15 Super Booster vitamin c serum color

It's still fine to use when it's light yellow, but once it starts to turn really dark yellow or orange, toss it! Using old Vitamin C serum probably won't cause you major harm, but it loses its potency (so what's the point?) and does have the potential to cause minor skin irritation.

The texture of this serum is light and sort of slippery (probably due to the Sodium Hyaluronate), and only slightly sticky. I'm currently using it as part of my morning routine—here's where it fits in:

  • Cleanse and dry face (ahhhh)
  • Apply Paula's Choice C15, wait a few minutes
  • Apply other moisturizers, sunscreen etc.
  • Have a wonderful day!

You can also mix a few drops of C15 with your moisturizer if you find it too harsh or sticky. One random but very important thing that needs to be noted: Paula's Choice C15 doesn't smell very good. Think hot dogs mixed with rotting carnations. Yum! The scent doesn't linger, but it does take a bit of getting used to.

Results: I'm on my second bottle of C15 now, and I think it works well to gradually reduce post-acne scars and keep skin looking supple and bright. So how does it compare to OST/C20? Here are the pros and cons:

Ways in which Paula's Choice C15 is superior to OST C20
  • Much gentler on the skin - no stinging for me
  • Less sticky
  • Better formulation of ingredients (Ferulic Acid/Vitamin E, no alcohol)
  • Slightly better packaging (a narrower opening lets in less air)

 Ways in which OST C20 is superior to Paula's Choice C15
  • C20 is much, much cheaper ($0.50 per ml vs. $2.40 per ml)
  • Results are quicker and more dramatic
  • More appealing scent. C20 smells kind of like sour oranges, Paula's Choice C15 smells hot-doggy

Bottom line: I think OST C20 is a better choice if you're on a tight budget or want quick/dramatic results, but Paula's Choice C15 is better if you have sensitive skin and/or want to maintain healthy, glowing skin (as opposed to burning the crap out of it for quicker results). I think I would be more likely to re-purchase C15 at this point, as I'm more in "maintenance mode" than "results mode" with my skin at the moment, but I would consider purchasing C20 again too. I actually want to try the new OST C21.5 next, which has a slightly nicer ingredients list than its predecessor. Will it be 1.5% more awesome? Stay tuned!

What do you think of Paula's Choice Resist C15 Super Booster? Do you have a favorite Vitamin C skincare product?

Disclosure: This post contains affiliate links. For more information, check out my full disclosure policy.


  1. Thanks for this review! I've tried the PC serum before but have resisted the OST one because my skin normally does not like Vitamin C at ALL. All those coupon codes and deals are ridiculously tempting though just to pick up some of my favorite PC items...I wonder if I can open a new account and use your referral....*does some sluething* ;)

  2. If your skin is sensitive to Vitamin C, I would definitely steer clear of C20. My skin tolerates Vitamin C well in general, but C20 still makes me tingle a little, lol.

  3. Lovely review! I agree to most of what you have written about the C20. I also used the Ole Henriksen youth activating serum which is super rich in vitamins and omega oils. That one is my fav for winter as it moisturizes instead of exfoliate. :) Thanks for sharing~

  4. Thanks for the suggestion! My skin has been mighty dry this winter, so the Ole Henriksen serum sounds great.

  5. Ahh, that sucks. I think "purging" is a real thing though. Didn't happen to me with Vitamin C, but my skin freaked the hell out when I first tried tretinoin and then died down after a couple weeks. Still... if the results aren't life-changing, is it really worth it? :P

  6. The C15 serum from Paula's Choice sounds like a nice Vitamin C Serum. I personally loved the OST C20 serum and now I'm trying the OST 21.5 serum. They cut down the ingredients of the latter to a minimum, maybe it would be nice to compare it with the one from Paula's Choice.

  7. The minimal ingredients in 21.5 is definitely appealing. The ingredients list is still pretty different to the Paula's Choice serum, but it will be interesting to see if 21.5 is less irritating than C20.

  8. I bought a bottle of this after trying a couple of the sample vials. I think it gave me deep cystic blemishes, which is weird because I used the samples with no problems. I did have the blemishes when I was quite sick with bronchitis, so maybe it was that more than the serum. I did really like using it, and I think it's an excellent formula. It looks like the OST serum is a much better price, but if you say it makes your skin tingle I think I'll kind of steer clear. I'm not fond of products that make my skin tingle (unless it's glycolic acid -- that I'm willing to put up with for some reason). I should try this stuff again.

  9. OST definitely gives me a bit of tingling. It's temporary (10 minutes maybe?) and not as strong as some other treatments - the Paula's Choice 10% AHA treatment gives me more of a tingle, just as an example. Deep cystic blemishes suck... I think Vitamin E is comedogenic for some people. Or maybe your skin was just angry because you were sick. Blah!

  10. totally just opened a new account so I could use your referral link and take advantage of the free shipping and coupon code to grab some of my BHA liquid! haha success! ;)