evidence: Colloidal silver does not treat infections when taken orally and can cause side effects [...] This claim was published in a Jan. 2020 blog post promoting the sale of colloidal silver products. The post went viral on Facebook in the same month, receiving more than 11,000 interactions on the platform within a week of publication. The article claims that colloidal silver effectively fights against any bacterial, fungal, or viral infection, calling it "a modern and fabulously effective treatment with virtually no side effects". [...] However, effective applications of silver as a medicine have been limited to topical treatments (such as application of a cream containing silver directly to a wound). There is no evidence that consuming or nasally spraying colloidal silver treats "any infection", as the claim states, or "supports the immune system". According to the U.S. National Institutes of Health, consuming colloidal silver or using it as a nasal spray can even cause health problems such as argyria, which is an irreversible blue-gray skin discoloration[9]. A 2018 review estimated that 70 – 1500 mg silver/kg body weight could induce argyria[10]. Colloidal silver can also interfere with the action of other drugs, such as thyroxine which is used to treat thyroid deficiency.