Any trauma to the skin, including UV and chemical exposure, heat, cuts, bruises, irritation, hair removal, and acne, can cause the inflammation that triggers the skin’s protective melanin response (hyperpigmentation).Hormones or genetics are the main triggers for the patches of discoloration known as melasma.In dark skin tones, the greater concentration of melanin in the skin means hyperpigmentation is more common and takes longer to fade.