The oligodynamic effect (from Greek oligos, "few", and dynamis, "force") is a biocidal effect of metals, especially heavy metals, that occurs even in low concentrations. This effect is attributed to the antibacterial behavior of metal ions, which are absorbed by bacteria upon contact and damage their cell membranes.
In modern times, the effect was observed by Carl Nägeli, although he did not identify the cause. Brass doorknobs and silverware both exhibit this effect to an extent.