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.
Melanin, the skin's brown pigment, is a natural sunscreen that protects tropical peoples from the many harmful effects of ultraviolet (UV) rays. UV rays can, for example, strip away folic acid, a nutrient essential to the development of healthy fetuses.