Hydroquinone

What it is

Hydroquinone is a simple two-hydroxyl benzene ring that blocks tyrosinase, the enzyme that starts pigment production, and is directly toxic to pigment-producing cells at higher doses. It was for decades the standard skin-lightening ingredient worldwide and is still prescribed by doctors in some countries for melasma. In the EU it may not be used in cosmetics, and it is the substance that arbutin and alpha-arbutin can release, which is why those two carry their own trace limits.

What it does well

• Highly effective at fading melasma and dark spots

  Hydroquinone remains the comparator against which other lightening agents are measured in clinical trials, and typically outperforms them. This is a statement about its potency under medical supervision, not an endorsement for cosmetic use in the EU, where it is prohibited.

  Strong evidence

Worth knowing

• Banned in EU cosmetic products

  Hydroquinone is listed as a prohibited substance in Annex II of the EU Cosmetics Regulation. The single narrow exception is professional artificial nail systems at 0.02% after mixing. Any skin-lightening cream sold in the EU containing hydroquinone is illegal.

  Matters most toAnyone buying skin-lightening products online or while travelling, where illegal hydroquinone creams are still widely sold.

• Can cause exogenous ochronosis with prolonged unsupervised use

  Long-term use, especially at high strengths and on deeper skin tones, can produce a permanent blue-black discolouration of the treated skin that is very difficult to treat. This is the main reason cosmetic self-treatment is considered unsafe.

  Matters most toPeople with deeper skin tones using imported lightening creams over months or years.

• The cancer concern is weaker than often claimed

  Concerns about carcinogenicity come mainly from high-dose rodent feeding studies; reviews of human topical use have not demonstrated an increased cancer risk. The EU ban rests chiefly on ochronosis, permanent depigmentation and the impossibility of supervising cosmetic use, rather than on proven human carcinogenicity.

  Matters most toAnyone weighing alarmist claims against the actual regulatory reasoning.

Where the EU stands

Sources (3)

Every link goes to the original: a journal, a PubMed record or an EU document.

1. [1]
   Regulation (EC) No 1223/2009 on cosmetic products, consolidated text, Annex II entry 1339 and Annex III entry 14

   EUR-Lex, European Union · 2025

   Hydroquinone is listed among substances prohibited in cosmetic products, with the sole exception of professional artificial nail systems at 0.02% after mixing.

2. [2]
   Exogenous Ochronosis

   Indian Journal of Dermatology · 2015 · doi:10.4103/0019-5154.169122

   Reviews exogenous ochronosis as a disfiguring and largely irreversible complication of prolonged topical hydroquinone use, most often reported with unsupervised high-strength products.

3. [3]
   The safety of hydroquinone: a dermatologist's response to the 2006 Federal Register

   Journal of the American Academy of Dermatology · 2007 · doi:10.1016/j.jaad.2007.02.020

   Argues that carcinogenicity concerns derive from high-dose oral rodent studies and that decades of supervised topical use have not shown increased cancer risk in humans.