I travel with a one-quart sized reusable plastic baggie containing 2-cups of a white powder mix in my check-in bag: one cup of sea salt and one cup of baking soda. It's for nasal irrigation.
EVERY SINGLE TIME TSA opens the bag and inspects it. Overseas? They have NEVER opened my bag to inspect it.
Annoying. I know darn well they are looking to see if it is drugs. Gotta love that mission creep . . .