It is VERY IMPORTANT to pay attention to the expiration date before you put anything on your face, just like how important it is to check expiration date for any kind of food you eat. This was educated from my mother, family, friends and the public since i was little. After years of following this rules, I had a second thought – how do production factory determine what is the expiration date? And what will happen if I really eat food after the expiration date? Will I get sick?