Carpal Tunnel Syndrome And Tarsal Tunnel Syndrome Carpal tunnel syndrome is a condition in which irritation of the wrist's median nerve causes tingling and numbness of the thumb,...learn more Â». In This Article.
1 Argyria-characterised by a metallic, slate-grey or blue-grey pigmentation. 2  The hyperpigmentation is most apparent in the UV-exposed areas of skin, especially the forehead, nose, and hands, as well as mucous membranes. 3  Argyria results from prolonged contact with or ingestion of silver salts.
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.