Ancient civilizations dropped silver coins into milk to prevent it from spoiling.

The preservation of milk with silver is based on the oligodynamic effect, a phenomenon first identified by Swiss botanist Karl Wilhelm von Nägeli in 1893. When silver comes into contact with liquid, it releases silver ions (Ag+). These ions are highly toxic to bacteria, viruses, and fungi because they bind to essential microbial proteins and disrupt their cell membranes.Historically, Phoenician records from as early as 1200 BCE mention using silver-lined vessels to keep water and wine pure. During the American westward expansion in the 1800s, pioneers frequently placed silver dollars in milk pails to delay souring. This was a critical survival tactic before Louis Pasteur developed pasteurization in 1862 or the widespread adoption of home refrigeration in the early 20th century.Modern research from institutions like the University of Arizona has confirmed that silver ions can effectively eliminate over 650 types of pathogens. Unlike many antibiotics, bacteria rarely develop resistance to silver because it attacks multiple cellular targets simultaneously. This ancient knowledge now informs modern medicine, where silver-impregnated dressings are used to treat serious burns and prevent infections in hospitals worldwide.