No, not anymore.
I shared a lipgloss with a friend, but then i got really nasty spots, since then, i don't share anything!
If someone wants to borrow something, i politley say that i have very sensitive skin, and no.
They are fine with that and don't ask me again.
If someone is over my house and we want to play with make up, i use disposable brushes, never dip twice. thats it. I don't let anybody touch my makeup on their own...no.