Why does Alpha Arbutin turn brown over t...

Why does Alpha Arbutin turn brown over time and is it still safe and/or effective to use if it does?

I have a half-used bottle of Alpha Arbutin 2% + HA concentrated serum that I got from The Ordinary maybe about 4 or 5 years ago. And I think I remember it turned brown-ish within a year, and has gotten a bit browner since then even though I tried my best to not leave it near sunlight or other light at first. I hate letting products go to waste though and am wondering if this is safe/effective enough to use on other parts of the body that are not the face? Such as on my legs, arms, etc? I'm curious also if anyone knows and can explain the chemistry of why this serum turned brown over time while my Niacinamide 10% + Zinc 1% serum from The Ordinary bought around the same time has stayed clear? If the Alpha Arbutin has become less effective or safe over time due to its turning brown, I was wondering if someone could explain exactly what happens to the chemistry of the Aalpha Arbutin over time to cause that? I heard that certain other types of clear serums that have turned brown/expired are unsafe to use on the skin once they've changed color, and I was wondering also if anyone remembered which ones and could explain what changed in its chemistry to make those serums unsafe past its expiration date? Thanks so much to anyone that's able to answer one or more of my questions! 😊❤ I've been curious about this for a while, and enjoy learning about the chemistry of these kind of things! 🐟

iibubblii

Dry/Resilient

Hi, I actually talked about this in one of my reviews. I didn't go in depth though. The color changing you see is present in all forms of vitamin c acids. It's due to it's nature to react to oxygen. This is called oxidation. When vitamin c is constantly exposed to the air we breathe in, it starts to lose its hydrogen atoms. This decreases the effectiveness of the acid. You can still use, but it will no longer be at the percentage you bought it at. That's why vitamin c serums are sold in small quantities. Think of it as you have a jar of smoke and every time you open it, some of the smoke escapes. Eventually you will have none left.

Butterbeans666

Oily/Resilient

Thank you! I didn't know that!

hdlums

Oily/Resilient

I saw a dermatologist video (Dr. Ingky), he said its their natural occurence that the product change color over the time. Its alright to use the product even after the color changes. From what ive learned, it is because of the oxidation, they absorb oxygen from the outside or exposed to light/heat. No worries still effective even not as effective as before the color changes. Thats the reason why serum always in a small bottle (estimated 1-2 months), or in dark amber glass bottle. Also, recommended not to keep serum in hot and humid places.

hdlums

Oily/Resilient

Hm im currently using alpha arbutin too, and their PAO is around 4-6months. i think it is better to discard the serum. Im afraid it might comes with the risk of reaction and allergic reaction. play it safe. sorry 🥺