Chloasma is a skin condition that causes dark, patchy discoloration on the face, most often during pregnancy. The term is used interchangeably with “melasma,” though “chloasma” specifically refers to pregnancy-triggered cases, sometimes called the “mask of pregnancy.” The patches are harmless but can be persistent, with up to 30% of pregnancy-related cases lasting years after delivery.
How Chloasma Looks on the Skin
Chloasma appears as symmetric, blotchy patches of darker skin, typically brown or grayish-brown. The discoloration follows one of three common facial patterns. The most frequent is the centrofacial pattern, seen in 50 to 80% of cases, which darkens the forehead, nose, upper lip, cheeks, and chin. The malar pattern is limited to the cheekbones, while the mandibular pattern affects the jawline and chin.
The patches have irregular borders and a net-like texture rather than a smooth, uniform color. They appear on both sides of the face in a roughly mirror-image distribution. Some people develop patches on the forearms or neck, but the face is by far the most common location.
What Happens Inside the Skin
Skin color comes from a pigment called melanin, produced by specialized cells called melanocytes in the outer layer of your skin. Melanocytes package melanin into tiny bundles and pass them to surrounding skin cells, which is what gives your skin its overall tone.
In chloasma, melanocytes in certain areas become overactive. They ramp up production of a key enzyme that converts an amino acid into melanin. The result is a localized surplus of pigment that shows up as dark patches. This overactivity is driven by a chain reaction: triggers like UV light or hormones flip on a master switch inside melanocytes that controls pigment-producing enzymes. Once activated, these enzymes churn out more melanin than the surrounding skin, creating the visible contrast.
Visible light, not just UV rays, also plays a role. High-energy visible light activates a receptor in melanocytes that increases the activity of the same pigment-producing enzyme, which is why standard sunscreens alone may not fully protect against chloasma.
Why Pregnancy and Hormones Are Major Triggers
Chloasma develops in an estimated 14.5 to 56% of pregnant women, with the wide range reflecting differences across ethnicities and geographic regions. The condition also affects 11.3 to 46% of people using oral contraceptives. The common thread is estrogen and progesterone.
Estrogen directly boosts melanin production through two routes. It binds to receptors inside melanocytes, switching on genes that produce pigment-making enzymes. It also attaches to receptors on the cell surface, triggering a rapid burst of chemical signals that further accelerate pigment output. Melanocytes in chloasma-affected skin actually have more of these hormone receptors than normal skin, making them especially sensitive to hormonal shifts.
Progesterone works through a separate but parallel pathway. It activates a signaling chain that ultimately turns on the same pigment-producing genes estrogen targets. Together, these two hormones create a powerful push toward excess melanin in susceptible skin. This explains why chloasma commonly appears during the second or third trimester, when hormone levels peak, and why hormonal contraceptives or hormone replacement therapy can trigger it outside of pregnancy.
Other Risk Factors
UV exposure is the single most important environmental trigger. Ultraviolet radiation increases the number of hormone-like signals in the skin that bind to receptors on melanocytes, amplifying pigment production. Even brief sun exposure can darken existing patches or trigger new ones.
Skin tone matters significantly. People with medium to olive complexions are most affected. In clinical studies, Fitzpatrick skin types III and IV (the scale ranges from I for very fair to VI for very dark) account for over 75% of cases. Hispanic and Latino populations make up the largest group in clinical trials at about 43%, followed by Asian (24%), White (16%), and Black (15%) participants. Women represent roughly 97% of cases in clinical research, though the condition does occur in men.
How Chloasma Is Diagnosed
Diagnosis is usually visual. The symmetric pattern and typical facial locations are distinctive enough that most dermatologists can identify it on sight. A Wood’s lamp, which emits ultraviolet light in a darkened room, helps determine how deep the excess pigment sits. If the patches become more pronounced under the lamp, the extra melanin is concentrated in the skin’s outer layer (epidermal). If they don’t change, the pigment has settled into deeper layers (dermal). A mixed pattern, where patches only slightly enhance, means both layers are involved. This distinction matters because epidermal pigment responds better to topical treatments than dermal pigment.
Treatment Options
The gold-standard topical treatment is a triple combination cream containing three active ingredients: a skin-lightening agent that inhibits melanin production, a retinoid that speeds cell turnover, and a mild corticosteroid that reduces inflammation. The FDA-approved version of this formula uses 4% hydroquinone, 0.05% tretinoin, and a low-potency steroid. Hydroquinone remains the most widely prescribed lightening agent worldwide, though it has been banned in cosmetics in Europe since 2001 due to safety concerns with unsupervised long-term use.
For people who cannot use hydroquinone or prefer alternatives, other lightening agents like azelaic acid, vitamin C, and kojic acid are commonly used, though they typically work more slowly. Chemical peels using glycolic acid can be combined with topical treatments to improve results.
An oral medication originally designed to control bleeding has emerged as a treatment option. At a dose of 250 mg taken two to three times daily for 12 weeks, it works by interfering with the signaling between UV-damaged skin cells and melanocytes. This is an off-label use, and the optimal approach appears to be 750 mg total per day for 12 consecutive weeks, though a lower dose of 500 mg daily may be acceptable for those who have difficulty sticking to the full regimen.
How Long It Lasts
Pregnancy-related chloasma often begins to lighten after delivery, but “often” is doing heavy lifting in that sentence. The fading process is slow, sometimes taking many months to reach normal skin tone. About 30% of pregnancy-induced cases persist long-term, with some lasting up to 10 years after delivery. Waiting for the condition to resolve on its own is not always a reliable strategy, especially since the patches can significantly affect quality of life and self-image.
Chloasma triggered by oral contraceptives may improve after stopping the medication, but the same unpredictability applies. Regardless of the original trigger, the condition tends to be chronic and relapsing. Even after successful treatment, patches can return with sun exposure or hormonal changes.
Sun Protection Beyond Standard Sunscreen
Because both UV and visible light drive pigment production, standard broad-spectrum sunscreens are not enough on their own. They block UV radiation effectively but offer limited protection against visible light. Tinted sunscreens containing iron oxides and pigmentary titanium dioxide fill this gap. These mineral pigments physically block visible light transmission. In one study, a tinted sunscreen with these ingredients achieved a visible light protection factor of 66, compared to essentially no visible light protection from an untinted sunscreen with identical UV-blocking ability.
Daily sunscreen use is the single most important step in both preventing new patches and keeping treated skin from darkening again. For anyone managing chloasma, choosing a tinted formula with iron oxides provides meaningfully better protection than a clear sunscreen with the same SPF number.