Melasma and Hyperpigmentation: What Causes It and What Works
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Melasma is a common acquired pigmentation disorder that causes brown or greyish-brown patches on the skin, most often on the face. It is sometimes called chloasma, particularly when it occurs during pregnancy, where it has historically been referred to as the "mask of pregnancy." The condition is chronic and tends to recur, especially with sun exposure or hormonal changes.
The patches typically appear in a symmetrical pattern. The most common distribution is centrofacial, affecting the forehead, cheeks, nose, upper lip, and chin. The patches are flat, not raised, and do not cause pain or itch.
Melasma is classified by depth. Epidermal melasma involves excess pigment in the outer layer of the skin and tends to appear brown with well-defined borders. Dermal melasma sits deeper in the skin and often looks greyish or bluish-brown with less distinct edges. Mixed melasma, the most common type, involves both layers. The depth of pigment matters because it influences how the skin responds to treatment.
According to the Australasian College of Dermatologists, melasma affects an estimated five million Australians, with a strong predominance in women. It can occur in all skin types but is more common in people with Fitzpatrick skin types III to V. While melasma can affect men, approximately 90 per cent of cases occur in women, reflecting the significant role that hormonal factors play in its development.
The terms melasma and hyperpigmentation are sometimes used as though they are interchangeable, but they describe different things. Hyperpigmentation is a broad, umbrella term for any condition in which patches of skin become darker than the surrounding area. It occurs when excess melanin is deposited in the skin.
Common forms of hyperpigmentation include:
- Post-inflammatory hyperpigmentation (PIH): Dark marks left behind after acne, eczema, burns, or other skin injuries. PIH is reactive and often fades over time, though the timeline can stretch to months or years.
- Solar lentigines (sun spots or age spots): Flat, brown spots caused by cumulative UV exposure. They tend to appear on sun-exposed areas and do not fluctuate with hormonal changes.
- Freckles (ephelides): Small, flat spots that darken with sun exposure and lighten in winter. They are genetically determined and most common in fair-skinned individuals.
Melasma is a specific type of hyperpigmentation, but it has distinct features. Its strong hormonal component sets it apart. Melasma patches are often larger and more diffuse than sun spots, tend to appear symmetrically on the face, and commonly fluctuate in intensity with hormonal shifts, seasons, and UV exposure.
The practical significance of this distinction is important. A brightening serum that fades a post-acne mark may have limited effect on hormonally driven melasma. Treatment plans for melasma need to account for its chronic, relapsing nature. A GP can help determine which type of pigmentation is present and recommend an approach tailored to the specific condition.
Melasma is a multifactorial condition. There is no single cause. Instead, several factors interact to trigger and sustain the overproduction of melanin.
Hormonal Influences
Hormones are the most significant driver of melasma. Oestrogen and progesterone stimulate melanocytes to increase pigment production. This explains why melasma commonly develops or worsens during:
- Pregnancy. Melasma affects an estimated 15 to 50 per cent of pregnant women, according to DermNet. The hormonal changes of pregnancy can trigger significant pigmentation changes that may persist after delivery.
- Oral contraceptive use. Combined hormonal contraceptives are a well-recognised trigger. Healthdirect Australia notes that melasma can develop in women taking the pill, and the pigmentation may not fully resolve after stopping.
- Hormone replacement therapy (HRT). Women using HRT during perimenopause or menopause may notice new or worsening melasma.
Ultraviolet Radiation
Sun exposure is both a trigger and an aggravating factor. UV radiation stimulates melanocytes to produce more melanin. This is particularly relevant in the Australian context, where UV levels are among the highest in the world. The Cancer Council Australia reports that Australia's UV index regularly exceeds the level at which skin protection is recommended.
Both UVA and UVB radiation contribute to melasma, and there is growing evidence that visible light, particularly high-energy blue light, can also stimulate melanin production in darker skin types.
Genetic Predisposition
Family history plays a role. Studies suggest that a significant proportion of people with melasma have a first-degree relative with the condition. DermNet notes that genetic susceptibility influences how melanocytes respond to hormonal and environmental triggers.
Other Contributing Factors
- Heat. Infrared radiation and ambient heat can worsen melasma independently of UV exposure.
- Certain medications. Some anti-seizure drugs and photosensitising medications can increase the risk of pigmentation changes.
- Thyroid conditions. There is an association between thyroid dysfunction and melasma, though the relationship is not fully understood.
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