Hy
Hydroquinone
HydroquinoneActive
Long-time gold standard for hyperpigmentation. Available by prescription in most regions; OTC use is increasingly restricted.
What it does
Hydroquinone inhibits tyrosinase, the rate-limiting enzyme in melanin synthesis. Effective for melasma and post-inflammatory hyperpigmentation, typically used in 2-4% formulations. Use is time-bounded — extended continuous use can cause exogenous ochronosis (paradoxical darkening). Most regimens are 3 months on / off.
The evidence, graded
expert consensusHydroquinone-treated skin is more prone to UV-driven pigmentation. Daily broad-spectrum SPF 30+ is required during use; without it, hyperpigmentation can rebound worse than baseline.Schwartz 2023 · StatPearls [Internet] ↗
expert consensusHydroquinone is absorbed through skin at 35–45% — much higher than most topicals. Pregnancy and breastfeeding guidance is to avoid it, even though existing studies have not shown harm.Bozzo 2011 · Canadian Family Physician ↗
Graded per the methodology: strong · moderate · emerging · expert consensus. A weak source on a strong claim gets the weaker label.
Pairs worth knowing
This page is public and indexed on purpose (unlike profiles and drops, which are unlisted) — it’s the citation behind shared ingredient cards, and it should be findable.
Want more like this?
Get Drop, free. Every flag cites its source, the app tells you when your routine is complete, and it helps you simplify — instead of selling you more products.