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Wednesday, October 14, 2026Index last updated Oct 14
The Index  ·  Benzene-1,4-diol tyrosinase inhibitor

Hydroquinone

Hydroquinone

Gold-standard topical depigmenting drug; banned/restricted in cosmetics in EU/CA and not legal as US OTC bleach.

StrongStrong drug-level efficacy for melasma; cosmetic use is prohibited or tightly restricted in major markets.
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Written byTheSkindex Desk
Reviewed byNot yet reviewed
Last updated17 Sept 2026
Sources4 cited

Hydroquinone remains the most efficacious topical agent for epidermal hyperpigmentation when used as a drug, typically 2–4% under dermatologic care[1]. It is not a routine cosmetic active in major markets.

What it does

It inhibits tyrosinase and is cytotoxic to melanocytes at treatment strengths, producing measurable clearing in melasma and post-inflammatory hyperpigmentation. Triple-combination therapy (hydroquinone + retinoid + steroid) outperforms many single agents in controlled trials[1].

Regulation — not a cosmetic default

In the EU, hydroquinone is prohibited in cosmetics (Annex II) except a narrow professional artificial-nail use under Annex III[2]. Health Canada’s Cosmetic Ingredient Hotlist restricts it to specified hair-dye, nail and cyanoacrylate uses — not leave-on skin lighteners[3]. In the US, CARES Act monograph reform deemed OTC skin-bleaching products containing hydroquinone not GRASE; they require an approved NDA and were to leave the OTC market after September 2020[4].

Practical take

Consumers looking for cosmetic brightening should prefer niacinamide, azelaic acid, tranexamic acid, kojic Acid or alpha-arbutin within regulated limits. Prescription hydroquinone belongs with a clinician, sunscreen, and a stop date to limit ochronosis risk.

Evidence by claim

Graded separately; the entry grade is the best-supported claim
Reduces melasma severity at prescription strengths (often in triple combination)[1]
Strong
Prohibited in EU leave-on cosmetics except narrow professional nail use[2]
Strong
Restricted on Health Canada Cosmetic Ingredient Hotlist; not for skin-lightening cosmetics[3]
Strong
US OTC skin-bleaching hydroquinone products are unapproved new drugs without an NDA[4]
Strong

Safety & limits

Source and region, always
0.02 % · professional artificial nail systems only — Annex II prohibition for general cosmetics; Annex III allows max 0.02% after mixing in professional artificial nail systems with warnings.[2] EU UK
0.3 % · oxidizing hair dyes; lower limits for nails/adhesives — Hotlist restricted: hair dyes ≤0.3%; nail products ≤0.1% (combined with p-hydroxyanisole); cyanoacrylate lash/brow adhesives ≤0.1%. Not permitted as a leave-on skin lightener.[3] CA
OTC skin bleaching drugs — OTC hydroquinone skin lighteners require FDA-approved NDA; CARES Act finalized non-GRASE status effective 23 Sep 2020.[4] US
drug/medical use — Exogenous ochronosis and irritation are known risks with prolonged or high-strength use; medical supervision required.[1] CA US EU UK

Sources · 4

Numbered as cited in the text
  1. [1]Sheth VM, Pandya AG. Melasma: a comprehensive update (efficacy context for hydroquinone/triple therapy). Journal of the American Academy of Dermatology (2011)doi:10.1016/j.jaad.2010.12.046review
  2. [2]European Commission. Commission Regulation (EU) 2021/1099 amending Annexes II and III (hydroquinone). Official Journal of the European Union (2021)regulation
  3. [3]Health Canada. Cosmetic Ingredient Hotlist — Hydroquinone (restricted). Health Canada (2024)regulation
  4. [4]U.S. Food and Drug Administration. FDA works to protect consumers from potentially harmful OTC skin lightening products. FDA Drug Safety Communication (2022)regulation

Revision history

17 Sept 2026Drafted by botTheSkindex Desk