It is a narcotic and may cause withdrawal symptoms if it is stopped too abruptly. Although Norco withdrawal can be quite unpleasant and uncomfortable, you can be assured that it is not life threatening. Norco withdrawal is possible in people who abuse Norco and in people who take Norco for a legitimate medical use.
Definition of melanin for English Language Learners. : a dark brown or black substance that is a natural part of people's skin, hair, and eyes.
Melanin is produced by special cells called melanocytes. More melanin is produced when the skin is not exposed to sunlight. Melanin ranges in color from yellow to brown to black. The stratum basale cells phagocytize the melanin produced by the melanocytes and it accumulates within them. Freckles and moles are seen where melanin is concentrated in one spot.