Hydroquinone

Important information about hydroquinone in the UK

Hydroquinone is not permitted as an ingredient in cosmetic skin-lightening products in the UK. The hydroquinone 4% formulations referenced on this page are unlicensed medicines and require individual medical assessment and prescription before regulated pharmacy supply when considered clinically appropriate. “Unlicensed” means that a particular medicine does not hold a UK marketing authorisation; it does not mean that appropriately prescribed and supplied use is automatically unlawful.

This page provides factual information about hydroquinone, its clinical uses, mechanism of action, available formulation types and principal safety considerations. It is not a guide to choosing a treatment or strength.

What is hydroquinone?

Hydroquinone is a topical depigmenting medicine used in clinician-directed treatment of certain forms of hyperpigmentation. It acts on the biological pathway responsible for producing melanin, the pigment that contributes to skin colour and the appearance of areas of excess pigmentation.

Medicinal hydroquinone should be distinguished from ordinary brightening cosmetics. Its use requires assessment of the type and cause of pigmentation, the condition of the skin and factors that may affect treatment suitability.

How does hydroquinone work?

Hydroquinone primarily inhibits tyrosinase, an enzyme involved in the conversion of tyrosine into melanin. By reducing activity within this pathway, it limits the formation of new pigment in the treated area.

This mechanism does not physically bleach the skin. It gradually affects melanin production while naturally pigmented epidermal cells move through the skin’s normal renewal cycle.

Response depends on several factors, including:

• The cause and depth of the pigmentation

• The concentration and formulation of hydroquinone

• Treatment consistency

• Skin sensitivity and tolerance

• Ultraviolet and visible-light exposure

• Inflammation or irritation during treatment

• The presence of an underlying or recurring trigger

Clinical indications for hydroquinone

A prescriber may consider hydroquinone for defined disorders involving excess epidermal pigmentation.

Melasma

Melasma causes symmetrical areas of brown or grey-brown pigmentation, commonly affecting the cheeks, forehead and upper lip. Hormonal factors, ultraviolet exposure, visible light and genetic susceptibility may all contribute.

Hydroquinone may be included in a medically supervised melasma treatment plan, often alongside strict photoprotection and measures intended to minimise irritation and recurrence.

Post-inflammatory hyperpigmentation

Post-inflammatory hyperpigmentation can develop after acne, eczema, injury, cosmetic procedures or other forms of skin inflammation. It occurs when inflammation stimulates excess melanin production.

Treatment suitability depends partly on whether the original inflammatory condition is adequately controlled. Excess irritation can aggravate pigmentation, particularly in darker skin tones.

Pigmentation associated with ultraviolet exposure

Hydroquinone may be considered for defined areas of pigmentation associated with cumulative ultraviolet exposure, including some solar lentigines commonly described as sun spots or age spots.

Pigmented lesions should be assessed appropriately before treatment. Hydroquinone is not a substitute for clinical evaluation of a new, changing or irregularly pigmented lesion.

Other localised hyperpigmentation

A clinician may consider hydroquinone for other forms of localised excess pigmentation after establishing the likely diagnosis. It is not intended as a general-purpose method of changing natural skin colour.

Hydroquinone concentrations

Hydroquinone products have historically been formulated in several concentrations. Lower-concentration products have been available as cosmetics in some countries, but hydroquinone is not permitted in cosmetic skin-lightening products in the UK.

The products referenced on this page contain hydroquinone 4%. The percentage describes the concentration of hydroquinone in the complete formulation. It does not, by itself, determine whether a particular product is appropriate for an individual.

Concentration should be considered alongside:

• Cream or serum format

• Complete inactive-ingredient profile

• Product vehicle and texture

• Skin type and barrier condition

• Other prescribed or non-prescribed products

• Intended application area

• Planned treatment duration

Products containing the same concentration are therefore not necessarily interchangeable.

Hydroquinone creams and serums

Hydroquinone can be incorporated into different formulation vehicles.

Cream formulations

Creams generally contain a mixture of water, emollients, emulsifiers and stabilising ingredients. Different hydroquinone creams may have distinct textures, supporting ingredients and positions within a wider treatment protocol.

Serum formulations

Serums may use a lighter liquid vehicle and can contain additional active or supporting ingredients. Some hydroquinone serums also contain L-ascorbic acid, commonly known as vitamin C.

A serum and a cream containing hydroquinone 4% should not be assumed to behave identically simply because the stated hydroquinone concentration is the same.

Multi-product systems

Some physician-directed skincare systems include hydroquinone products alongside cleansers, exfoliating products, moisturisers and sun protection. The presence of hydroquinone means that the prescription elements of the system still require individual clinical assessment.

Treatment duration and clinical review

Hydroquinone is generally used for a defined treatment period rather than continued indefinitely without review. The appropriate duration depends on the diagnosis, response, skin tolerance and prescribed treatment plan.

A prescriber may review:

• Whether pigmentation is responding as expected

• Whether irritation is adequately controlled

• Whether treatment should continue, pause or stop

• Whether maintenance should use a different approach

• Whether the diagnosis requires reassessment

Continued or repeated use should follow clinical guidance.

Principal safety considerations

Hydroquinone can cause dryness, redness, stinging, irritation or contact sensitivity. Excessive inflammation may worsen post-inflammatory pigmentation rather than improve it.

Some formulations contain sulphites, including sodium metabisulphite, which can cause hypersensitivity reactions in susceptible individuals.

Prolonged, inappropriate or unsupervised use has been associated with exogenous ochronosis, a rare condition involving persistent blue-black or grey-blue skin discolouration. Medical advice should be sought if unexpected darkening or discolouration develops.

Other important considerations include:

• Avoiding application to broken, inflamed or acutely irritated skin unless specifically instructed

• Following the prescribed application area, frequency and duration

• Avoiding unnecessary combinations with irritating active ingredients

• Using appropriate broad-spectrum sun protection

• Reporting persistent irritation or unexpected pigmentation changes

• Keeping the product away from the eyes and mucous membranes

• Following any storage instructions supplied with the medicine

Hydroquinone is not normally used during pregnancy or breastfeeding. Individual suitability and contraindications must be assessed by the prescriber.

Hydroquinone and sun protection

Ultraviolet and visible-light exposure can stimulate melanin production and contribute to the persistence or recurrence of hyperpigmentation.

Broad-spectrum sun protection is therefore an important part of most pigmentation-management plans. It does not replace medical treatment, but inadequate photoprotection can limit the response to treatment and increase the likelihood of pigmentation returning.

Hydroquinone and tretinoin

Hydroquinone and tretinoin affect pigmentation through different biological mechanisms. Hydroquinone reduces melanin formation, while tretinoin influences epidermal cell turnover and can affect the penetration and activity of other topical ingredients.

They may be prescribed within the same clinical protocol in selected cases. Using them together can also increase dryness and irritation, so the combination requires individual assessment and medical supervision.

Further information is available in Tretinoin and Hydroquinone: Should They Be Used Together?.

Frequently asked questions

Is hydroquinone illegal in the UK?

Hydroquinone is prohibited in cosmetic skin-lightening products in the UK. This is distinct from the controlled prescribing and pharmacy supply of an unlicensed hydroquinone medicine for an individual patient following medical assessment.

Is hydroquinone available over the counter in the UK?

The hydroquinone 4% medicinal formulations referenced here are not over-the-counter cosmetics. They require individual medical assessment and prescription when considered clinically appropriate.

What does hydroquinone 4% mean?

It means that hydroquinone accounts for 4% of the formulation. Products sharing this concentration may still differ in their vehicle, texture, supporting ingredients and intended position within a treatment protocol.

Is hydroquinone a skin bleach?

Hydroquinone inhibits a biological pathway involved in melanin production. In medical use, it is applied for defined areas or disorders of excess pigmentation; it is not intended as a general method of changing natural skin colour.

How quickly does hydroquinone work?

Response varies according to the cause and depth of pigmentation, formulation, treatment consistency, tolerance and light exposure. Progress and treatment duration should be assessed against the individual clinical plan rather than a guaranteed timetable.

Can hydroquinone make pigmentation worse?

Irritation can contribute to post-inflammatory hyperpigmentation, particularly in skin that is prone to pigmentary changes. Unexpected darkening, persistent inflammation or blue-black discolouration requires medical review.

Are all hydroquinone 4% products the same?

No. Equal concentration does not establish identical formulation or clinical use. Creams, serums and products occupying different positions in a treatment system may have different vehicles and supporting ingredients.

What is the difference between hydroquinone and arbutin?

Hydroquinone is used medicinally and the 4% products referenced here require prescription. Arbutin is used in non-prescription cosmetic formulations and is not equivalent to prescription hydroquinone.

Related clinical information

• Tretinoin and hydroquinone: should they be used together?

• Obagi Clear and Clear FX: formula and UK status compared

• Hydroquinone alternatives for hyperpigmentation

• Medical-grade skincare and hyperpigmentation

Last updated: September 2026.