Melasma is driven by overstimulation of melanocytes (the pigment-producing cells) by UV and visible light, hormonal influences (oral contraceptive pill, hormone replacement therapy, pregnancy, sometimes called the "mask of pregnancy"), and genetic predisposition. It is now understood that visible light, not just UV, stimulates melanin production, which is why chemical sunscreens alone are often insufficient for melasma control.
How is it diagnosed?
Diagnosis is based on distribution, appearance, and a detailed history of sun exposure, hormonal use, skincare, and prior treatments. Dermoscopy helps assess pigmentation depth. Wood's lamp examination provides additional information in certain skin types. Biopsy is rarely required but may be performed to exclude conditions such as lichen planus pigmentosus or drug-induced pigmentation.
