Allah’s Apostle was asked regarding ghee (cooking butter) in which a mouse had fallen. He said, “Take out the mouse and throw away the ghee around it and use the rest.”
Ghee is more viscous than the usual oil, so it can be used after throwing away the part touched by the mouse. Going into the scientific details, ghee allows less diffusion so the impure particles of the mouse won’t be able to travel very far. Oil, however, would have to be thrown away if a mouse fell in it.