Melasma: The role of hormones in skin pigmentation.

Also referred to as "chloasma", the melasma is due to a disruption in the pigmentation process (melanogenesis). The melanin, pigment responsible for the natural colouration of the skin, is overproduced in certain areas, leading to the appearance of brown spots. These spots most often appear on the face.

According to the American Academy of Dermatology, only 10% of melasma cases affect men.

Women with darker skin types and/or who are pregnant are more likely to develop melasma. Indeed, this type of skin disorder is due to hormonal fluctuations.The increase in oestrogen levels, particularly during pregnancy or with the use of certain medications (e.g. the pill), can lead to brown spots. These are exacerbated by exposure to the sun's UV rays. This hyperpigmentation phenomenon is also known as the "mask of pregnancy". It often disappears spontaneously after childbirth.

There are different types of melasma depending on the layer of the skin presenting the brown spots:

• The epidermal melasma: Brown spots only affect the superficial surface of the epidermis;

• The dermal melasma: The spots form at the deep layer of the skin called the dermis;

• The mixed melasma: Hyperpigmentation spots appear on both the superficial and deep layers of the skin.

Formerly known as cholasma or "pregnancy mask", melasma is a symmetrical hyperpigmentation of the face, ranging from light brown to dark brown. It occurs during the second trimester of pregnancy in 45 to 75% of women. It also appears in about a third of women taking oral contraceptive pills.

Depending on the location of the brown spots, there are 3 types of melasma:

• The centrofacial melasma: The spots are clustered in the T-zone, upper lip, and chin area;

• Themalar melasma (the most common): The spots are located only on the nose and cheeks;

• The mandibular melasma: Clustering of spots on the lower jaw.

According to several studies, melasma is believed to be caused by theincrease in levels of female hormones (oestrogen and progesterone) as well as beta-endorphin. Indeed, these hormones are powerful stimulants of melanogenesis. Furthermore, women who develop hyperpigmentation following the use of contraceptive pills are more likely to develop melasma during any potential future pregnancy.

How can melasma be prevented? The best prevention remains sun protection. Therefore, it is advised to limit the times exposed to the sun, avoid exposure during the most intense hours (between 11am and 3pm), wear clothing and hats for protection, and of course apply a sunscreen daily, even on cloudy days.