The Skinny : CosRx Triple C Lightning Liquid

Woo, we’ve got a guest post today! Patyof — whom you already know and love from the comments — brings us a report on a C serum from CosRX. But is it good tho? LET’S FIND OUT!

I’m still not 100% sure what “bright” skin is supposed to look like, although I know vitamin C can help you get it. I know it’s not an entirely empty marketing term–  brightening products are supposed to do specific things, like even out skin tone, fade hyperpigmentation, and counteract sallowness. (Plus less-visible but equally important things like fighting photodamage). But like its cousin “glowy” there’s still something about “brightening” that makes it feel like a case of “I need to see it.”

A couple of months after finishing my vitamin C Suspension from The Ordinary (HORRID texture, no results), and mid-way through a sample of Drunk Elephant’s C-Firma Day Serum (meh), I got an absolutely panicked-sounding email from K-beauty retailer Soko Glam. Something along the lines of: “NOW BACK IN STOCK! LIMITED STOCK! SMALL BATCH! BUY THE COSRX TRIPLE C LIGHTNING LIQUID SERUM NOW!!!”

Photo from, wherein the product is held aloft Holy-Grail-style. Insert “ahhhhhhhh” choir sfx.

Honestly, I don’t remember signing up for this alert email, but props to the SokoGlam marketing team for doing their job well, because I immediately snatched it up. At $27 for 1 oz on their site, it’s certainly not the most expensive impulse by, so I filed this one under Treat Yourself™.

After a couple weeks of daily use, with my complexion looking better and better in some kind of general but undefinable way, I finally realized—oh, THIS is “bright” skin! Y’all—I’ve seen and I believe! With 20.5% Ascorbic Acid, it’s definitely on the punchier side of the vitamin C product spectrum. It also touts special ingredient “black chokeberry,” which purports to add hydration and help to stabilize the Ascorbid Acid, plus familiar friends like licorice root extract (for more brightening) and sodium hyaluronate (a.k.a. hyaluronic acid).

Photo from SokoGlam

As with any active, the standard recommendation is start with light concentrations and infrequent use, and CosRx specifically recommends using this product at night… but naturally I didn’t listen to any of that. To me, vitamin C serums are daytime products, since they help counteract sun damage — although it is also an acid, so definitely don’t leave home without sunscreen if you do use it in the day. I didn’t notice any irritation aside from a teeny tiny itty bitty little touch of tingling the first few times I applied it, but my skin also tends to be rather nonreactive — so if you know you’re at all sensitive to acids, it’s probably smart to follow CosRx’s “work your way up to it” advice, either by using it every other day at first, or mixing a few drops into your moisturizer.

My main issue with this product is the same one I have with all the other vitamin C products out there — OXIDATION. Per CosRx’s recommendation, I kept my Lightning Liquid tightly sealed in its dark bottle, inside its box, and stored it in a closed refrigerator door. Luckily my apartment is small, but it was still a real pain to walk out to the kitchen, grab my serum, go back to the bathroom, apply, and then take the serum back to the fridge! Agh. Even with this responsible storage system, I still found the color started to change after about 3 months, by which time I had only used about half of the bottle, even with near daily use! I kept thinking that I wish I had a roommate to split it with — then I’d be able to use up the whole product before it started spoiling and everyone could enjoy the great results.

I also found the formula a bit sticky. The stickiness dries down fairly quickly, and when I was more circumspect with *exactly* how many drops I used, and I applied to a well-hydrated base, I noticed this less, so this isn’t a deal breaker for me, but may be something to be aware of if that kind of texture stuff bugs you.

But anyway — will I buy again? Almost definitely! I’ve got a few other vitamin C serums teed up to try, but at the end of the day, CosRx’s Triple C Lightning Liquid was the one that finally convinced me that bright skin is a for-real thing. Plus, the price isn’t so bad, and with vitamin C products that can be a real issue (looking at you, Skinceuticals! Grr). If only I could convince them to make a 0.5 oz size…

Tried it? Love it or nah? Got a fave topical C product? Discuss!