Your epidermis contains cells called melanocytes that store and produce a dark color (pigment) known as melanin. In response to light, heat, or ultraviolet radiation or by hormonal stimulation, the melanocytes produce more melanin, and that’s why your skin darkens. Estrogen and progesterone sensitivity are also associated with the condition. This means birth control pills, pregnancy, and hormone therapy can all trigger melasma. Stress and thyroid disease are also thought to be causes of melasma.
There are three types of melasma and they have to do with the depth of the pigment.
The three types are:
Epidermal melasma has a dark brown color, a well- defined border, appears obvious under black light and sometimes responds well to treatment.
Dermal melasma has a light brown or bluish color, a blurry border, appears no differently under black light and doesn’t respond well to treatment.
3. Mixed melasma
Mixed melasma, which is the most common of the three, has both bluish and brown patches, shows a mixed pattern under black light and shows some response to treatment.