You notice it first in bright light — a smudge of brown across your cheeks that looks almost symmetrical, like it was painted on. You didn’t have it a year ago. Now it won’t fade no matter how much concealer you use.
Melasma causes happens when melanocytes, the pigment-producing cells in your skin, go into overdrive. The two main drivers are radiation — ultraviolet, visible, or infrared light — and hormones, but genetics, thyroid function, certain medications, and even stress all shape who develops it and how stubborn it becomes.
What Melasma Actually Is
Melasma is a common acquired skin disorder that shows up as bilateral, blotchy, brownish pigmentation on the face, most often across the cheeks, forehead, nose bridge, and upper lip. It used to be called chloasma, and older generations still know it as the “mask of pregnancy.”
Roughly 90% of cases occur in women, with only about 10% affecting men. Globally, it’s estimated to affect somewhere between 1.5% and 33% of the population, and it shows up in 15% to 50% of pregnant women — a huge range that reflects how much skin tone, sun habits, and genetics affect who gets it.
Dermatologists classify it by how deep the pigment sits:
- Epidermal melasma — pigment in the outer skin layer, brown with sharp, well-defined edges. Usually responds best to treatment.
- Dermal melasma — pigment deeper in the dermis, giving a blue-gray tone. Harder to treat because it sits below the layers most creams can reach.
- Mixed melasma — a combination of both, and the most common presentation in people who’ve had melasma for years.
Quick takeaway: Melasma isn’t one single thing — it’s a spectrum of pigment depth, and that depth is part of why some people’s melasma responds to treatment fast while others fight it for years.
Sun and Light Exposure: The Biggest Trigger
If there’s one cause that shows up in every dermatologist’s explanation, it’s light. Ultraviolet light from the sun is arguably the single most significant trigger — UV exposure stimulates melanocytes to produce more melanin, which is why melasma often worsens in summer and fades somewhat in winter.
What surprises most people is that UV isn’t the whole story. Visible light and infrared (heat) radiation can also drive melasma, which is why some people notice flare-ups after time near a hot stove, a sauna, or even a laptop screen close to their face — not just after a day at the beach.
Even brief sun exposure can trigger or worsen melasma in people who are already prone to it — a few minutes without sunscreen on a cloudy commute is sometimes enough to undo weeks of fading.
Hormones: Why It’s Called the “Mask of Pregnancy”
Hormonal shifts are the second major pillar of melasma. An increase in estrogen and progesterone, which occurs during pregnancy, is thought to trigger melasma, which is exactly why the nickname stuck.
It isn’t limited to pregnancy, though. Melasma occurs mostly in women, especially due to hormonal changes caused by pregnancy or the use of contraceptive treatments. It’s also been observed in people using oral contraceptive pills containing estrogen and progesterone, and hormone replacement therapy carries a similar risk.
The mechanism seems to run deeper than estrogen and progesterone alone. Elevated melanocyte-stimulating hormone, which can rise during chronic stress, also plays a role, and even cortisol has indirect effects on melanocyte behavior through its influence on inflammatory pathways in the skin.
Genetics: Is Melasma Hereditary?
If your mother or grandmother had melasma, pay attention to your own skin in the sun. Studies show that 40 to 60 percent of melasma patients have a family history of the condition — a strong enough pattern that most dermatologists now treat genetic predisposition as a baseline risk factor, not a coincidence.
Skin tone matters here too. Melasma is most common in people who tan easily or have naturally brown skin — Fitzpatrick skin phototypes III and IV — and less common in people with very fair skin or very deep skin tones. That middle-of-the-spectrum skin has enough melanocyte activity to overreact to triggers, but not the deeper baseline pigment that would otherwise mask it.
Thyroid Problems and Other Medical Links
This is where a lot of melasma content stops too early. Thyroid function is genuinely tied to pigmentation. If your thyroid gland develops a problem, this may increase your risk of developing melasma, and sometimes treating the thyroid issue clears the pigmentation up on its own.
Hypothyroidism specifically has been linked to increased skin pigmentation issues, since the disrupted metabolism and hormone fluctuations can make melasma more persistent. Clinical case-control research has directly investigated this connection in women with melasma, reinforcing that thyroid hormone levels genuinely influence melanocyte activity rather than just correlating by chance.
Melasma also clusters with other endocrine conditions more often than people expect. It’s more often diagnosed in patients with polycystic ovary syndrome, insulin resistance, or thyroid dysfunction — a pattern worth mentioning to your doctor if your melasma is unusually stubborn or paired with irregular cycles.
Quick takeaway: If melasma appears alongside fatigue, weight changes, or irregular periods, it’s worth asking your doctor for a thyroid or hormone panel — treating the underlying issue sometimes fades the pigmentation as a side effect.
Medications That Can Trigger Melasma
A handful of drug categories are consistently underreported as melasma triggers:
- Antiseizure medications — drugs that prevent seizures, such as clobazam, may act as a cause of melasma.
- Photosensitizing medications — medications that make your skin more sensitive to sunlight, including some retinoids, certain antibiotics, and some blood pressure medications, can trigger melasma.
- Synthetic estrogen — diethylstilbestrol, a synthetic form of estrogen sometimes used in prostate cancer treatment, has shown a similar pattern between increased estrogen and melasma.
If you’ve started a new prescription in the months before melasma appeared, that timing is worth mentioning to whoever prescribed it.
Can Stress Really Cause Melasma?
This one gets dismissed too often as folk wisdom, but the biology holds up. Elevated cortisol from chronic stress activates melanocyte-stimulating pathways, and chronic psychological stress raises both cortisol and melanocyte-stimulating hormone levels, both of which can stimulate melanin production, while also promoting systemic inflammation and vasodilation that activates the vascular trigger pathway.
That vascular piece explains something patients notice constantly but rarely get answered: why melasma seems to darken after drinking alcohol, eating spicy food, exercising intensely, or feeling emotionally stressed — all of these cause vasodilation, expanding the blood vessels that feed the melanocytes.
To be fair to the skepticism: the stress-melasma link is still considered somewhat controversial in the research, even though some findings support it. Stress alone probably won’t cause melasma in someone with no other risk factors — but in someone already predisposed, it’s a believable amplifier.
Who’s Most Likely to Get It
Pulling every risk factor together, melasma tends to concentrate in a fairly specific profile:
| Risk Factor | Why It Matters |
|---|---|
| Women, ages 20–40 | Hormonal exposure window is highest |
| Medium-to-olive skin tones (Fitzpatrick III–IV) | Enough melanocyte reactivity without deep baseline pigment |
| Family history | 40–60% of patients have a relative with melasma |
| Pregnancy or hormonal birth control | Estrogen/progesterone surges |
| Sun-heavy climates or lifestyles | More cumulative UV/visible light exposure |
| Thyroid or endocrine conditions | Hormonal disruption independent of reproductive hormones |
The Emotional Toll Nobody Talks About
Most articles on melasma causes stop at biology and skip the part patients actually feel. A systematic review pooling nearly 3,000 melasma patients found a pooled depression prevalence of 43.4%, and a separate cross-sectional study found a prevalence of 33.3% for depression and 21.6% for anxiety among melasma patients.
It may run both directions. Persistent psychological stress caused by living with melasma often leads to depression, and depression itself can raise cortisol and pro-opiomelanocortin levels — both of which have melanogenic potential and can increase melanin content in melanocytes. In other words, the visible patches and the emotional strain can feed each other in a loop, which is exactly why dermatologists increasingly recommend screening for mood symptoms alongside skin treatment, not after it.
Can You Prevent Melasma?
You can’t fully control genetics or hormones, but you can control exposure. Daily broad-spectrum sunscreen — ideally one containing iron oxide, since it blocks visible light in addition to UV — is the single highest-leverage habit. Reviewing new prescriptions with your doctor, managing thyroid health, and being mindful of stress and known vascular triggers like alcohol and intense heat round out a realistic prevention approach. None of this guarantees melasma won’t appear, but it meaningfully lowers how severe or persistent it becomes.
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FAQ Section
What is the main cause of melasma?
There isn’t a single cause — the two primary drivers are light exposure (UV, visible, and infrared) and hormonal changes, layered on top of a genetic predisposition that determines who reacts strongly to those triggers.
Is melasma genetic?
Genetics plays a real role. Roughly 40 to 60 percent of melasma patients have a family history of the condition, though it still requires a trigger like sun exposure or hormonal change to actually appear.
Can stress cause melasma?
Stress is more of an amplifier than a root cause. Elevated cortisol from chronic stress activates melanocyte-stimulating pathways, but the research linking stress directly to new-onset melasma is still considered somewhat inconclusive.
Does melasma mean I have a hormonal imbalance?
Not necessarily an imbalance, but it does reflect hormonal sensitivity. Pregnancy, oral contraceptives, and hormone replacement therapy are all recognized triggers, and persistent cases sometimes prompt a thyroid or hormone workup.
Can thyroid problems cause melasma?
Yes. Thyroid gland problems can increase the risk of developing melasma, and treating the underlying thyroid issue sometimes clears the pigmentation.
Can men get melasma?
Yes, though it’s less common. Approximately 90% of melasma cases occur in women, with only about 10% affecting men.
Why is melasma called the “mask of pregnancy”?
Because the surge in estrogen and progesterone during pregnancy is thought to trigger it, and the pigmentation often appears in a mask-like pattern across the central face.
Does melasma go away on its own?
Sometimes, especially pregnancy-related melasma, which can fade months after delivery as hormone levels normalize. Melasma tied to sun exposure, medication, or thyroid issues is more likely to persist until the underlying trigger is addressed.
