If there is hot dairy being cooked in a pan, and I pour crushed garlic salt from a plastic container over it while it is cooking, is there an issue with using that crushed garlic salt container with meat?
It is for this reason that essentially it is preferable to have different spice containers for milk and meat. However it is not required, and if it was already done the spices can be used for the other type.
Livushei Oz 88-2(8), Badei Hashulchan 92-165, Pischei Halacha pg. 235.