Today, various kinds of silver compounds, or devices to make solutions or colloids containing silver, are sold as remedies for a wide variety of diseases. Although most colloidal silver preparations are harmless, some people using these home-made solutions excessively have developed argyria over a period of months or years. High doses of colloidal silver can result in coma, pleural edema, and hemolysis. Silver is widely used in topical gels and impregnated into bandages because of its wide-spectrum antimicrobial activity. The anti-microbial properties of silver stem from the chemical properties of its ionized form, Ag+. This ion forms strong molecular bonds with other substances used by bacteria to respire, such as molecules containing sulfur, nitrogen, and oxygen. Once the Ag+ ion complexes with these molecules, they are rendered unusable by the bacteria, depriving it of necessary compounds and eventually leading to the bacteria's death. Silver is now considered to be a bioaccumulating carcinogen and thus its use in food is not advised. In India and Pakistan, foods, especially sweets, can be found decorated with a thin layer of silver known as vark. Silver as a food additive is given the E number E174 and is classed as a food coloring. It is used solely for external decoration, such as on chocolate confectionery, in the covering of dragÃ©es and the decoration of sugar-coated flour confectionery. In Australia, it is banned as a food additive.