miles581•14d agoMost Upvoted

Found a stat about vitamin C serums that stopped me cold

I was reading through a study from the Journal of Clinical and Aesthetic Dermatology last weekend. Turns out vitamin C loses about 50% of its potency within 2 weeks if the bottle is clear glass or not sealed right. I had been telling clients to just keep them on the bathroom counter. Now I'm telling everyone to buy the opaque airless pump bottles or keep them in the fridge. Anyone else find out their go-to product was basically useless after a month?

2 comments

2 Comments

benflores14d agoMost Upvoted

Hold on, that study's numbers are a little off. Most vitamin C formulations use ascorbic acid which is already pretty unstable, but losing half its strength in two weeks on a bathroom counter is way too fast unless it's in a completely clear bottle with no stabilizers. A better-formulated serum with vitamin E and ferulic acid in an opaque bottle can actually hold its potency for months at room temp. The real kicker is that even the good ones start to break down once you open them, but it's more like a slow decline, not a cliff drop. You're right to recommend airless pumps and opaque bottles, but telling people to toss a serum after a month is probably overkill if it's a decent brand. And for the love of skincare, keep it out of the direct sunlight and away from a steamy bathroom shower.

black.mark14d ago

Look I gotta push back on this @benflores because that "slow decline" thing is exactly what gets people into trouble. My cousin left her Drunk Elephant C-Firma in her car for like a week last summer and that stuff turned straight up orange brown, not even a subtle change. Nobody's serum is made entirely of magic if it sits in a warm bathroom or gets exposed through a pump that lets air back in. The industry literally has expiration dates for a reason, and if you're paying $60 for Skinceuticals I'd rather be safe than sorry tossing it at 30 days. Even with ferulic acid and vitamin E you're still fighting oxidation the second oxygen hits it, so that "months at room temp" claim only works if you barely open the bottle.