In India and Pakistan, foods, especially sweets, can be found decorated with a thin layer of silver known as vark. Silver is also used as a food coloring (E174).
Silver plays no known natural biological role in humans, and possible health effects of silver are a subject of dispute. Silver itself is not toxic but most silver salts are, although it is now suspected by some to be a bioaccumulating carcinogen.
Silver can also be absorbed into the circulatory system and become deposited in various body tissues leading to a condition called argyria which results in a blue-grayish pigmentation of the skin, eyes, and mucous membranes. Although this condition does not otherwise harm a person's health, it is disfiguring and usually permanent.
Rarely, very high levels of silver (due to excessive doses of colloidal silver) have been known to be correlated with seizures and other neurological problems and kidney damage.
Low levels are seen in patients with thyroid dysfunction.