Hydroquinone is commonly used to treat melasma and hyperpigmentation. However, prolonged or unsupervised use can rarely cause exogenous ochronosis, a condition in which the skin becomes darker instead of lighter.
What Is Exogenous Ochronosis?
Exogenous ochronosis causes blue-black or slate-gray discoloration, most often on the cheeks, temples, or neck.
It is an acquired skin condition caused by topical exposure and is different from alkaptonuria, an inherited disorder that can affect other parts of the body.
How Does It Appear?
The condition often develops gradually.
Early signs may include redness or worsening pigmentation that resembles melasma. Because patients may assume their melasma is worsening, they may apply more hydroquinone and unintentionally aggravate the condition.
As it progresses, the skin may develop:
- Blue-gray or black discoloration
- A speckled or stippled appearance
- Small, dark, caviar-like bumps
- Colloid milia in advanced cases
Can Low-Strength Hydroquinone Cause It?
Although exogenous ochronosis was once associated mainly with high-strength hydroquinone, cases have occurred with concentrations as low as 2%, particularly after years of regular use.
Risk may also be harder to predict with counterfeit or unregulated products because the actual concentration may differ from the label.
Who Is at Risk?
Exogenous ochronosis was initially reported most often in Black patients, particularly in South Africa. However, it has since been documented across many skin tones and ethnic backgrounds, including Asian, Hispanic, and White patients.
The condition may be underdiagnosed because its early stages closely resemble melasma.
How Is It Diagnosed?
A dermatologist may use dermoscopy to identify patterns suggestive of ochronosis. In uncertain cases, a skin biopsy may be needed.
Under the microscope, ochronosis typically shows curved, banana-shaped pigment deposits that are not seen in melasma.
How Is It Treated?
Treatment can be difficult, and discoloration may persist even after hydroquinone is stopped.
The first step is to discontinue hydroquinone. Additional management may include:
- Daily broad-spectrum sunscreen
- Protective clothing and shade
- Topical retinoids or other pigment-regulating ingredients
- Carefully selected chemical peels
- Certain laser treatments in appropriate patients
Laser treatment must be used cautiously, particularly in deeper skin tones, because it may worsen pigmentation.
When to See a Dermatologist
Seek evaluation if you notice:
- Pigmentation becoming darker while using hydroquinone
- Blue-gray or black discoloration
- A speckled pattern or small dark bumps
- Pigmentation that no longer improves with treatment
- Worsening after increasing the strength or frequency of use
Do not increase hydroquinone use without medical guidance. Early recognition may help prevent further progression.
References
- Schleicher S, Doss N, Ali SE, Desai SR. “Exogenous Ochronosis: Dark Skin Patches.” Dermatology Advisor. January 7, 2025.
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