Medical Encyclopaedia › Melasma (short definition)
In brief: Melasma, also called chloasma, is an acquired pigmentation disorder with irregular light to dark brown patches, usually symmetrical on the cheeks, forehead, upper lip or chin. It is harmless but is often perceived as distressing.
Causes
Melasma results from overactivity of the pigment-producing melanocytes. The most important trigger is sunlight, including visible light. Hormones play a major role: melasma often occurs during pregnancy (“mask of pregnancy”) or with hormonal contraception. Women and people with medium to darker skin types are affected more often.
Prevention
Consistent sun protection is the most important measure: a broad-spectrum sunscreen with a high sun protection factor every day, ideally tinted, as iron oxides also block visible light. Hats and avoiding intense midday sun complement the protection.
Treatment and evidence
Topical lightening agents are used, such as hydroquinone (prescription-only in Germany), often combined with a retinoid and a mild corticosteroid, as well as azelaic acid, niacinamide or tranexamic acid. Oral tranexamic acid is also being investigated in studies; it is not approved for this purpose and is not suitable for everyone because of a possible risk of thrombosis. Peels and laser procedures can help but carry the risk of worsening pigmentation disorders. Relapses are common; a permanent cure cannot be guaranteed.
When to see a doctor?
New or changing pigmented patches should be examined by a dermatologist to rule out other causes such as age spots or, in rare cases, malignant changes.
Related terms in the encyclopaedia
Melanin, Melanocytes, Hyperpigmentation, Sun protection factor (SPF), Tranexamic acid, Niacinamide, Azelaic acid, Chemical peel
Sources
- American Academy of Dermatology (AAD): Melasma – Diagnosis and treatment
- Verordnung (EG) Nr. 1223/2009 über kosmetische Mittel (Regelungen zu Hydrochinon)
Note: This article is for general information and does not replace advice, diagnosis or treatment from a doctor or pharmacist. Last updated: October 2026.