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.
Also called pigment, melanin is a substance that gives the skin and hair its natural color. It also gives color to the iris of the eye, feathers, and scales. In humans, those with darker skin have higher amounts of melanin.By contrast, those with less pigment have lighter or more fair skin coloring.Melanin, sometimes referred to as a chemical, is formed as part of the process of metabolizing an amino acid called tyrosine.In the skin, melanin is formed by cells called melanocytes.y contrast, those with less pigment have lighter or more fair skin coloring. Melanin, sometimes referred to as a chemical, is formed as part of the process of metabolizing an amino acid called tyrosine. In the skin, melanin is formed by cells called melanocytes.