1. Introduction Old white surgical scars turn dark brown in the summer sun because the disorganized connective tissue of a scar is structurally distinct from normal skin and reacts unpredictably to ultraviolet radiation. The melanocytes surrounding and within the scar tissue can become hyper-reactive to sunlight, aggressively overproducing melanin in a misguided attempt to protect … Read more
1. Introduction Mosquito bites leave behind dark hyperpigmented scars due to a dermatological process known as post-inflammatory hyperpigmentation. The acute inflammation and subsequent scratching of the bite disrupt the basal layer of the epidermis, triggering melanocytes to overproduce melanin, which then drops into the deeper dermal layers where it becomes trapped and appears as a … Read more
1. Introduction Face freckles fade completely during the dark winter months because they are entirely dependent on continuous exposure to ultraviolet radiation to maintain their pigment. Without the stimulating effect of summer sunlight, the melanocytes in these specific areas stop overproducing melanin, and the existing pigment naturally degrades as the skin cells undergo their standard … Read more
1. Introduction The dark vertical line on the stomach, known clinically as linea nigra, occurs due to a localized increase in melanin production stimulated by fluctuating hormone levels, specifically estrogen and melanocyte-stimulating hormone. While commonly associated with pregnancy, this hyperpigmentation can be triggered in non-pregnant individuals by hormonal contraceptives, polycystic ovary syndrome, or natural endocrine … Read more