[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Other dermatological medicines](https://durgical.com/en/pharmacology/classes/other-dermatological-medicines/) › Hydroquinone

# Hydroquinone

## Other dermatological medicines?

Other dermatological medicines

A tyrosinase-blocking skin lightener used under supervision for melasma; unapproved over-the-counter creams can cause permanent darkening (ochronosis).

Updated Nov 1, 2026

## Quick facts

**Group**
[Other dermatological medicines](https://durgical.com/en/pharmacology/classes/other-dermatological-medicines/)

**Target**
Tyrosinase, the first enzyme of melanin synthesis in melanocytes

**Used for**
Melasma and other dark patches

**Key effects**
Irritation or contact dermatitis · Rash

**Monitor**
Skin colour response · Bluish-black darkening

**ATC**
D11AX11

No doses: the clinician sets them by the current guideline.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

Hydroquinone (1,4-dihydroxybenzene) lowers melanin production by inhibiting tyrosinase, the first enzyme of melanin synthesis in melanocytes. It also breaks down melanosomes and, through reactive oxygen species, can damage melanocytes, so dark patches gradually lighten.

- Cream is applied to dark patches
- Hydroquinone inhibits melanocyte tyrosinase
- Less melanin; melanosomes break down
- Dark patches gradually lighten

## Indications

- Melasma and other dark patches (in some countries as a prescription combination with a corticosteroid and tretinoin) [Melasma →](https://durgical.com/en/conditions/melasma/)

## Adverse effects

### Common

- Irritation or contact dermatitis
- Rash

### Serious (rare, important)

- Exogenous ochronosis: blue-black darkening of the skin that may be permanent
- Facial swelling and serious skin reactions with unapproved products

## Contraindications

- Hypersensitivity to hydroquinone

## Key interactions

**Unlabelled or imported skin-lightening creams**
May contain mercury or hidden hydroquinone; they are avoided.

**Topical corticosteroid and tretinoin (prescription combination)**
Used together for short-term melasma treatment under supervision.

## What is monitored

- Skin colour response
- Bluish-black darkening (ochronosis) or irritation

## Administration and safety

- Used only on dark patches and only under a clinician's supervision.
- Daily sun protection is part of treatment.
- Products are checked for a proper label and ingredient list.

## Pregnancy and breastfeeding

Use in pregnancy or breastfeeding is discussed with the treating clinician first.

## Nursing care

- Ask about any imported or unlabelled skin-lightening creams.
- Teach daily sun protection and to stop and report new darkening, rash or swelling.
- Explain that approved treatment is short-term and supervised.

## Pharmacokinetics

**Absorption**
Applied to the skin

## Memory aid

HYDROquinone: Hits tYrosinase; overuse = Darkening (Ochronosis).

## Test yourself

Think of the answer, then tap the question to see it.

## Which enzyme does hydroquinone inhibit?

Tyrosinase, the first enzyme of melanin synthesis.

## What paradoxical darkening can hydroquinone cause?

Exogenous ochronosis, a blue-black discoloration that may be permanent.

## Which hidden toxic metal has been found in some imported skin-lightening creams?

Mercury.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/hydroquinone/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## Connections

## Related drugs 2

- [Azelaic acid](https://durgical.com/en/pharmacology/azelaic-acid/)
- [Tretinoin](https://durgical.com/en/pharmacology/tretinoin/)

## Related conditions 1

- [Melasma](https://durgical.com/en/conditions/melasma/)

[← Back to the class: Other dermatological medicines](https://durgical.com/en/pharmacology/classes/other-dermatological-medicines/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [FDA works to protect consumers from potentially harmful OTC skin lightening products](https://www.fda.gov/drugs/drug-safety-communications/fda-works-protect-consumers-potentially-harmful-otc-skin-lightening-products) (U.S. Food and Drug Administration, 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=D11AX11) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/hydroquinone/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/hydroquinone/