By Dr. Alan Brooks · September 15, 2026
Pure vitamin C is effective but unstable. Exposed to air and light, it oxidizes and turns the serum orange or brown.
Stable derivatives are gentler and last longer in the bottle, though they work more slowly.
Pairing vitamin C with ferulic acid and vitamin E helps it stay stable and work better against daytime sun damage.
Use it in the morning, under sunscreen, and keep the bottle closed and out of the bathroom window.
