Can you catch anything from trying on lipstick and other make-up in the stores where they leave testers out?

You bet your bippy. You can get , oral thrush, and any number of respiratory ailments from them. Byp putting those items on your face, opt for the back of the hand if you just want to check the shade. If you really want to see what it looks like on you- most of the reputable makeup counters have single sample blister packs. Of course those are for the more expensive lines of makeup, but if you really must put it on your face, that is the only way to go.