Written September 8, 2026. Research covered through 2026-06-30.
On this page: What a recent comparison found · Different measurements can give different answers · What to check when shopping · A different formula to compare · Keep reading
What to know: Compare the whole routine and the type of marks studied, not just the ingredient on the label.
Two dark-spot serums may both have research behind them without a clear winner. The studies can use different formulas, sunscreens and ways of measuring change. That makes a simple “this ingredient is best” claim difficult to support.
What a recent comparison found
A June study compared two serum-and-sunscreen routines for marks left after acne. Both improved the main pigmentation score. The routine containing 2-MNG did not show a clear advantage over the thiamidol routine on that main measure.
Some other results favored it, but the formulas and sunscreens differed. The study cannot tell us that one ingredient alone caused the difference. La Roche-Posay supported the work, and several authors worked for L’Oréal. Read the study
Different measurements can give different answers
An earlier thiamidol trial found improvement in doctors’ pigmentation ratings. Participants’ overall ratings and digital color measurements did not show a clear difference between the groups.
Beiersdorf funded the study, supplied the creams and employed one author. That does not erase the positive finding. It does mean the full result is more mixed than a short advertisement might suggest. The paper first appeared online in January, before the six-month window covered by this collection. Read the earlier study
What to check when shopping
Look for a study of the product’s formula and the kind of marks it claims to improve. Check whether the comparison changed the serum alone or an entire routine.
Be cautious with a promised fading timeline. The result in a study group cannot tell you exactly when your own marks will change. A different-looking photo is also not proof that a product produced the same result measured by researchers.
These papers do not settle which serum you should buy. They do help you recognize a better product explanation: it names what was tested, describes the result clearly and leaves room for uncertainty.
A different formula to compare
This section contains an affiliate link. As an Amazon Associate, GlowPal earns from qualifying purchases.
Anua Niacinamide 10% + TXA 4% Serum, 30 ml is included for readers comparing niacinamide-and-tranexamic-acid formulas with the ingredients discussed above. It is a different formula, not a substitute for the products tested. These papers do not establish its results or a fading timeline.