To stop your shampoos, cremes and everything else you pack in a bottle wile traveling from leaking out and ruining your baggage, squeeze the bottle while screwing on the lid. This will get some of the air out of the bottle itself and creates a tiny vacuum. That vacuum, in other words, suction, will keep your bottle drip-free for your travels.
Of course, anything liquid you bring in carry-on luggage will have to go in a plastic sealed bag anyway (thanks to the TSA) but this helps. It's a good idea to plastic wrap the bottles in your checked luggage too, just in case.
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