From users, and from around the web with the source linked.
A user says their skin absolutely rejected The Ordinary Niacinamide 10% + Zinc 1%, suspects the zinc, and advises patch testing first.
“My skin absolutely rejected that The Ordinary niacinamide formulation, and I suspect the Zinc component, so do a patch test first.”
Their acne marks got noticeably smaller using it twice a week.
“I like Naturium's tranexamic topical acid 5%. My acne spots noticeably got smaller after using it 2x a week”
Has used it for years: a backlit glow no other vitamin C gives them, oxidises less easily and moisturises, but it's potent and not for beginners.
“It makes my skin glow like the setting sun. I have used it for years”
A user saw a big improvement in skin quality pairing The Ordinary Hyaluronic Acid 2% + B5 with the brand's copper peptide serum.
“I noticed a big improvement in my skin quality combining The Ordinary HA/B5 serum with their Multi-Peptides + Copper.”
An esthetician who says Great Barrier Relief changed their skin and strengthened their barrier; starting tretinoin, they never got flaky.
“I highly recommend trying Krave Beauty Great Barrier Relief Serum. It has changed my skin”
Uses the DIVE-IN serum with the toner; some call it just water, but they find it simple and not irritating.
“I use torriden dive in toner + serum, some people complain it’s basically just water but I find it very simple and not irritating”
Many tiny whiteheads after a week on acne-prone skin.
“I am experiencing many tiny whiteheads after a week of using the ordinarys niamicide and zinc..”
A user finds their skin looks bright and radiant every time they use The Ordinary Niacinamide 10% + Zinc 1%, calling it underrated for about $6.
“The Ordinary’s Niacinamide is about $6. Every time I use that serum my skin looks bright & radiant.”
Layers it with a milky toner in winter for extra hydration on oily, dehydrated skin.
“It's probably not hydrating enough on it's own during the winter, I use it along with the Skin1004 Centella Ampoule.”
On their fourth 95 ml bottle: the only barrier serum that works for their very oily, acne-prone skin on adapalene; it doesn't break them out despite its thicker texture.
“it's the only barrier serum that works for my acne prone skin”
Helped their skin texture when used in the morning alongside a retinoid routine.
“I've tried all three and they all helped me with my skin texture”
Did little beyond mild hydration and made no difference to their face, so they use it on their arms.
“I agree that the CosRx doesn’t do much beyond mild hydration. I ended up using it on my arms because it made no difference to my face.”
Finished a bottle and felt it didn't do much beyond hydration.
“I used Cosrx 6 Peptide skin booster and felt like it didn't do much after finishing the bottle.”
Used alone, the Niacinamide 10% + Zinc worked wonders and practically cleared their dark spots.
“I was using The Ordinary Niacinamide 10% + Zinc 1%, and it worked absolute wonders. It practically made all my dark spots disappear.”
Nice for hydration but no noticeable anti-aging results.
“I do like the Cosrx because it is very nice for hydration and I layer it in when I need extra”
Moved it to body care and isn't sure they'll repurchase.
“I’ve elevated the CosRX to body care.”
Currently using it but not loving the results so far.
“I am using the Cosrx one but not loving it.”
Used the COSRX Vitamin C 23% serum every other day and broke out badly within days; it cleared once they stopped.
“I tried the COSRX Pure Vitamin C 23% Serum every other day for a few weeks, but within days, I started to break out BAD.”
A great budget replacement for Estée Lauder ANR.
“discovered the brand Missha has a great dupe called Time Revolution Night Repair. It’s great!”
Loves it for calming redness and evening out skin tone.
“you should try adding the BoJ calming barrier serum, I LOVE it for redness and evening out tone.”
Has done wonders for their dehydrated, flaky skin under adapalene.
“Cosrx 6 Peptide Serum has done wonders for my dehydrated, flaky skin.”
Tried both Glow Serum and Glow Deep and neither helped their skin.
“I've tried both the Glow Serum and Glow Deep Serum, and both of them did not help my skin in any way.”
They find it a really good product, unlike the 4/10 rating in the post.
“I guess it varies from person to person and from skin to skin :) I find it to be a really good product.”
An oily-dehydrated user's holy-grail routine uses the Torriden Dive-In serum as the base hydration step.
“This is my base hydration step.”
They use Beauty of Joseon Glow Deep Serum religiously to balance their harsh azelaic and retinal creams; gentle and replenishing.
“I have been using their Ginseng cleaning oil, Rice Milk toner, and Glow Deep Serum religiously.”
A user tried the Torriden serum twice and found it genuinely useless.
“I tried the Torriden serum twice in the past, but it felt genuinely useless”
Repairing an over-exfoliated barrier, a user's skin is healing with Torriden serum and Illiyoon cream, but feels tight for up to an hour after applying.
“for few minutes to hour of putting serum and moisturizer my skin feels tight”
Somewhat brightening but sometimes breaks them out if used all over the face.
“Finally the Numbuzin no 5+ serum was somewhat brightening, but sometimes breaks me out if i use it all over my face.”
Two months of the numbuzin No.5 serum after the toner pads makes their skin glow.
“I use the toner pads followed by the Numbuzin 5 vitamin c serum. I have been using these for about 2 months now. It makes my skin glow!”
Wrecked their sensitive, reactive skin at full strength and still reacted when diluted with cream.
“Yo la probé pocas veces con toda la concentración y me destrozaba la piel (tengo piel sensible y reactiva)”
An oily-skinned user finds the Torriden Dive-In serum lightweight, quick-absorbing, gentle and fragrance-free; they wake up less oily, though it may be too light for very dry skin.
“It’s lightweight, absorbs quickly, and feels hydrating, but there was never a dramatic “wow, my skin looks different” moment.”
Impressed with the PDRN Pink Peptide Serum; on their sensitive skin it causes only a brief tingle and redness.
“I’ve been impressed with the original PDRN serum. My skin is sensitive, and while this does make my skin tingle/redden, it doesn’t last more than a moment or two”
A user's skin didn't tolerate the Anua Niacinamide 10 + TXA 4 serum.
“My skin didn’t like it. Too much niacinamide for me!”
A dry, sensitive user rated the Anua Niacinamide 10 + TXA 4 serum 1/10: it was too harsh and took weeks to repair their barrier.
“Sure enough, it was way too harsh for my dry, sensitive skin type! It took weeks to repair my skin barrier after using it.”
Several months with no visible result, so they gave up on vitamin C.
“started with Cosrx Vitc 23 for several months and switched to Dr Brenner 20% After that I gave up and stopped using”
Sensitive skin has stuck with Drunk Elephant C-Firma for 8 years, gets compliments on their bare skin, and likes the newer mix-at-home formula that resists oxidizing.
“I have sensitive skin and this is the only product I’ve stayed consistent with for 8 years and I get compliments all the time on my bare skin .”
Their holy grail for keeping their barrier healthy.
“krave beauty great barrier relief is my holy grail product to keep my skin barrier healthy”
A user who stopped using The Ordinary HA finds the Torriden Dive-In serum much better.
“Torriden deep dive for me personally has been much better.”
The numbuzin No.5 serum makes their complexion less dull, especially around the mouth. Their long-term holy grail.
“Numbuzin is super good in making face complexion better, less dull.”
Has used the snail mucin essence for years and always comes back to it.
“I am using cosrx snail mucin essence for years and recently added hada labo premium ..loving it ✨”
Plumps and hydrates and helps with fine lines.
“I really love the ordinary HA. It plumps the skin and hydrates, good for teeny lines.”
Used almost daily for 1–2 years; since stopping they notice their skin slowly losing its glow.
“I was using CosRx 23% Vit Cfor about 1-2 years almost daily in the morning”
Mature skin had its best glow and most even tone ever, but the bottle felt underfilled for the price.
“Before the bottle was empty, I realized my skin had never looked better as far as an overall glow and even skin tone.”
Part of a peptide routine that brightened their skin with no irritation, unlike vitamin C.
“I use Ordinary's multi-antioxidant in the morning and in the evening I use CORSX peptide booster.”
Loves it; other vitamin C serums they tried were just meh.
“Sunday Riley was the first one I tried and I also love that one! I went through a few other vitamin C serums that were just meh”
After repurchasing it no longer gives the same hydration and is kind of irritating their skin.
“i had been using snail mucin for like 2+ years, stopped, recently repurchased it but it's not giving me the same level of hydration it used to... in fact it's kind of irritating my skin”
A dehydrated, sensitive-skinned user says the Glow Serum has given them the best results of any serum.
“I've tried plenty of serums over the years but this is the one that has given me the best results.”
Alternates between the essence and the cream, one of the few AB items to survive their skincare purge.
“I alternate between the essence and the cream. I like it's in a tube now too!”
Has repurchased the snail mucin essence for about a decade.
“There are only 2 items I have repeatedly purchased for the past decade or so. The first one is the Hada Labo lotion and the second is the CosRx Snail mucin essence.”
The snail mucin has stayed in their routine for seven years, with the cream for travel.
“The snail mucin is the only thing that has stayed consistent in my routine for the past seven years. I use the cream when I travel”
Has used the Paula's Choice C15 Super Booster and finds it an excellent mid-range alternative to SkinCeuticals CE Ferulic.
“Pretty sure I can mention Maelove Glowmaker and Paula's Choice C15 Booster. They are mid-range and excellent dupes to skinceuticals. I have used both and keep them refrigerated.”
After a month, a dry-leaning combo user found the Torriden Dive-In serum sank in instantly with no pilling under EltaMD and kept skin holding moisture longer than The Ordinary HA.
“Applied it and it just sank in. No waiting, no pilling, no sticky layer.”
Uses KraveBeauty Great Barrier Relief before moisturizer when their skin is sensitive; it helped heal waxing wounds without lasting marks despite being scar-prone.
“If you want to add something healing I use the Great Barrier Relief serum from Krave Beauty before my moisturizer at night when my skin is feeling sensitive.”
A month of nightly use improved oil, clogged pores and breakouts.
“I started using it about a month ago, and I’ve already noticed a nice difference in my skin, specifically in oil production, clogged pores, and breakouts.”
Part of the routine that's working well for their dry, sensitive, mildly rosacea-prone skin.
“I use the Sunday Riley CEO every other day in the AM.”
Calls Paula's Choice C15 Super Booster a fantastic vitamin C serum.
“Paula's Choice C15 Super Booster is a fantastic Vitamin C serum that's easy to get in Canada.”
A user's skin has been breaking out with daily white pimples since starting the Anua Peach Niacinamide Serum.
“I’m currently using the peach serum by anua”
Cleared dry patches along their smile line within a week on normal-oily sensitive skin.
“I first tried the Moisture Boost Serum and after about a week, the dry patches resolved.”
About a month in it started a run of cystic pimples.
“I added a 10% niacinaminde (Paula's Choice) to my routine, hoping to shrink some enlarged pores, and after about a month my first cystic acne pimple arrived.”
A user had the same burning reaction and puffy face from the Light On Serum and needed antihistamines for three days.
“I had the very same reaction with exact symptoms, along with waking up with extra puffy eyes and face.”
A darker-skinned user finds the Glow Deep Serum great for hyperpigmentation on its own.
“Glow deep is great for hyperpigmentation and I use it alone.”
One of two barrier serums that help their dryness.
“The aveeno oat one and the ordinary barrier serum both are good.”
Great Barrier Relief fixed bad dehydration and peeling after a beach trip; still using it five years later.
“I had really bad dehydration and peeling that didn’t get better after a beach trip about five years ago, tried Great Barrier Relief and haven’t looked back since”
A brown-skinned user found the Glow Deep Serum did little alone, but paired with Hada Labo Shirojyun it drastically faded their pigmentation over six weeks.
“I started using the BOJ Glow Deep serum along with my very minimal routine of a basic cleanser and sunscreen, and it didn't really do much.”
A four-year Glow Deep Serum buyer says it's the only thing that lightens their PIH.
“I just hope it works as well as the prior formula, since it’s the only thing that lightens my PIH.”
A user switching from The Ordinary HA finds the Torriden Dive-In serum a little lighter but no noticeably different, and may go back for price.
“The torriden is a little lighter, but truthfully I like both!”
A user's skin broke out like crazy from the Torriden Dive-In serum.
“Torriden made my skin break out like crazy :(”
On their second bottle and enjoys how it makes skin feel plump, though results are temporary.
“this is my second bottle I think. I really enjoy how it makes my skin feel a bit plump.”
Has used it for a couple of years and likes it, but wants a cheaper or better replacement.
“i’ve been using this serum for a couple years and i like it but i wanna replace it i think.”
Says it is so good and leaves skin feeling nice, though it smells like sausage water.
“Oh this one is so good. My skin feels so nice after this! Also yes it smells like sausage water”
Paired with a niacinamide serum, their skin tone is so even and bright now.
“I use numbuzin's vitamin C serum and pair it with a niacinamide serum from Axis-Y. This combo works absolute wonders on my skin. My skin tone is so even and bright now”
Remembers it working pretty well for their acne marks a year or two ago.
“I tried the numbuzin no 5 serum around a year or two ago and I remember it working pretty well”