Silver-resistance, allergy, and blue skin: truth or urban legend?

Medical and non-medical uses of silver are increasing. While the health benefits of silver therapy are widely claimed, few studies address the possible side effects of resistance, allergy, or skin discoloration. In this manuscript, a review of silver absorption, mechanism of action, allergy, microbial resistance and skin changes is presented. The ideal silver-delivery system is unknown. Most studies of side effects are animal or laboratory studies, which may not correlate with human experience. There is little correlation between serum silver levels, end-organ deposition and cytotoxic effects. The multiple mechanisms of antimicrobial action make true resistance unlikely. In microbes, genotypic resistance does not necessarily confer phenotypic resistance. Most cases of argyria occur from occupational exposure or from ingestion of colloidal silver rather than from topical application. Although toxicity, resistance and chronic skin changes are a theoretic concern, the lack of reported side effects despite widespread silver use is reassuring.