What Causes Melasma? Understanding the "Mask" on Your Face

What causes melasma to develop?

Melasma happens when melanocytes — the cells responsible for skin color — receive signals that cause them to overproduce pigment in patches. Three overlapping factors drive this:

Sun exposure is the most consistently implicated trigger. UV light (and even visible light and heat) stimulates melanocytes directly. This is why melasma typically worsens in summer and in sun-heavy climates, and why daily broad-spectrum sunscreen is the foundation of any melasma management plan 1Ref 1Sarkar R, Handog EB, Das A, Bansal A (2023).Topical and Systemic Therapies in Melasma: A Systematic Review.Pathophysiology of melasma; role of sun/UV exposure; topical treatment options including hydroquinone, azelaic acid, and peels; sunscreen as foundational management.

Hormonal changes are the second major driver. Pregnancy is the most well-known trigger — melasma during pregnancy is sometimes called the 'mask of pregnancy' or chloasma. Estrogen and progesterone sensitize melanocytes. Hormonal contraceptives (the pill, patch, or ring) and hormone therapy can trigger or worsen melasma for the same reason.

Genetics play a clear role. Melasma tends to run in families and is significantly more common in people with naturally deeper or olive skin tones (Fitzpatrick types III–VI), though it can affect any skin tone.

Who is most likely to develop melasma?

Melasma is considerably more common in women than in men, though men do develop it. It is especially prevalent in people who:

• Spend significant time in the sun or live at high altitude or in tropical climates
• Are of Latin American, Southeast Asian, South Asian, Middle Eastern, or African descent
• Have a family history of the condition
• Are in their reproductive years and using hormonal contraception or are pregnant

It can appear at any age after puberty, and people who take certain medications (some anticonvulsants, thyroid medications, and phototoxic drugs) may also be at increased risk.

Why is melasma so persistent?

Melasma is notoriously difficult to fully clear because the melanocytes remain sensitized long after the initial trigger resolves. Even with effective treatment, patches often return with significant sun exposure. Hormone-triggered melasma (from pregnancy or contraceptives) may fade after the hormonal exposure is removed, but this is not guaranteed and can take months.

Sun avoidance and daily broad-spectrum sunscreen — including protection against visible light and heat, not only UV — are the non-negotiable foundation that makes other treatments work. Without consistent sun protection, even the most effective topical therapies tend to lose ground [1, 2].

What treatment options does a dermatologist consider?

A dermatologist can confirm the diagnosis, assess the depth of pigmentation (epidermal versus dermal melasma responds differently to treatment), and recommend a tailored plan. Options that a clinician might discuss include [1, 2]:

• Topical lightening agents — hydroquinone (available by prescription) remains the most studied first-line agent; used in cycles to minimize risk of side effects. Azelaic acid, kojic acid, and tranexamic acid are alternatives or additions.
• Topical retinoids — enhance the effect of lightening agents and promote skin cell turnover; not recommended during pregnancy.
• Niacinamide — reduces melanin transfer to skin cells; can be a useful adjunct with a favorable safety profile 3Ref 3Boo YC (2021).Mechanistic Basis and Clinical Evidence for the Applications of Nicotinamide (Niacinamide) to Control Skin Aging and Pigmentation.Niacinamide as an adjunct treatment for hyperpigmentation including melasma; favorable safety profile; mechanism of reducing melanin transfer.
• Chemical peels — superficial peels (glycolic acid, lactic acid) help in epidermal melasma.
• Laser and light-based treatments — require careful selection based on skin tone; in darker skin, aggressive laser treatment can trigger post-inflammatory hyperpigmentation and worsen the condition.

Self-treating with harsh over-the-counter brightening products can worsen certain types of melasma or cause new pigment problems, so professional guidance matters — particularly for anyone with deeper skin tones.

How is melasma different from other types of dark spots?

Several conditions produce facial discoloration that looks similar:

Post-inflammatory hyperpigmentation (PIH) follows a specific insult — a pimple, rash, or skin injury — in the same spot. More localized than melasma and lacks the symmetrical cheek/forehead pattern.

Solar lentigines (sun spots / liver spots) are well-defined, round or oval spots common after age 40. Usually more discrete than melasma's diffuse, irregular patches.

Drug-induced hyperpigmentation can follow certain medications and may appear in unusual locations.

A dermatologist can distinguish these using Wood's lamp examination (to assess pigment depth) and dermoscopy. A skin biopsy is rarely needed but can be done if the picture is unclear.

Any patch that is raised, has an irregular or rapidly changing border, bleeds, or looks very different from the rest of the discoloration warrants dermatology evaluation to rule out other diagnoses.

What special considerations apply during pregnancy?

Melasma is extremely common during pregnancy and often appears or worsens in the second trimester. Many first-line treatments — hydroquinone, retinoids, certain chemical peels — are not recommended during pregnancy. Niacinamide and azelaic acid are generally considered acceptable options in pregnancy, but any treatment decision should be made with a clinician 3Ref 3Boo YC (2021).Mechanistic Basis and Clinical Evidence for the Applications of Nicotinamide (Niacinamide) to Control Skin Aging and Pigmentation.Niacinamide as an adjunct treatment for hyperpigmentation including melasma; favorable safety profile; mechanism of reducing melanin transfer. Daily broad-spectrum sunscreen and sun-protective clothing are appropriate and important for everyone, including during pregnancy.