HYDROQUINONE

📋 Quick facts

Description: HYDROQUINONE — skin lightening, tyrosinase inhibitor — EU-prohibited for general/OTC cosmetic use, permitted only in narrow professional contexts (see eu_restriction_note).

All Functions: skin lightening, tyrosinase inhibitor — EU-prohibited for general/OTC cosmetic use, permitted only in narrow professional contexts (see eu_restriction_note)

Quick Facts:

• Category: active
• Regulatory Note: Prohibited in the EU

Proven Benefits At A Glance:

• Hydroquinone is a skin-lightening agent used to treat melasma, post-inflammatory hyperpigmentation, age spots, and other pigmentation disorders
• It works by inhibiting tyrosinase, an enzyme involved in melanin production
• A U.S. ban on over-the-counter hydroquinone products has raised questions about its safety
• In clinical trials, hydroquinone reduced melasma severity by 33-43% over 90 days
• Alternative depigmenting agents like thiamidol and tranexamic acid show comparable effectiveness
• Hydroquinone use during breastfeeding is not well-studied; some experts recommend caution with long-term use
• Mild to moderate adverse effects have been reported in clinical studies

⚗️ Chemical Overview

Hydroquinone appears as light colored crystals or solutions. May irritate the skin, eyes and mucous membranes. Mildly toxic by ingestion or skin absorption. Hydroquinone is a benzenediol comprising benzene core carrying two hydroxy substituents para to each other. It has a role as an antioxidant, a cofactor, a carcinogenic agent, a mouse metabolite, a human xenobiotic metabolite, an Escherichia coli metabolite and a skin lightening agent. It is a benzenediol and a member of hydroquinones. The CIR Expert Panel concluded that hydroquinone is safe at concentrations of less than or equal to 1% for cosmetic formulations designed for discontinuous, brief use followed by rinsing from the skin and hair. Hydroquinone is safe for use in nail adhesives and in artificial nail coatings, as a polymerization inhibitor, that are cured by LED light. Hydroquinone is unsafe for use in other leave-on cosmetic products.

Source(s): Cosmetic Ingredient Review (CIR), CAMEO Chemicals, ChEBI, via PubChem

📊 Comedogenicity

🛡️ Safety rating

Safety tier is a starting heuristic from regulatory status and comedogenic rating, not a dermatological verdict — see our Terms for the full disclaimer. Research confidence reflects how many real cited studies back this ingredient, not the strength of their findings.

🤰 Pregnancy Safety Note

Skin lightening agent. 25-35% systemic absorption. Insufficient pregnancy safety data. Avoid during pregnancy.

🌍 Regulatory Status