Yes. Before sharing the mascara, you must make sure that your friend's eyes did not get infected. If your friend's eyes get infected, then your eyes are easily to get infected also because you know the bacteria thrive in moist conditions, it's a really easy way to pass on eye infections to your eyes. Even though the eyes of your friend's did not get infected, you can just share the mascara only once; do remember that do not make the sharing the mascara a habit, otherwise there are more possibilities that your eyes get disordered, including the pink eyes. Considering the health of the eyes of you and your friends, you had better not share mascara with each other. By the way, after using the mascara for 6 months, you have better throw them away because there should be some bacteria attached on the mascara. Good luck.