How important is the expiration date on makeup and skincare? The expiration date is not randomly picked. It’s based on the ingredients and the preservatives in the makeup or lotion. There are two major functions of preservatives; to keep the active ingredients rich in activity and to prevent bacterial and fungal overgrowth. For active ingredients, oils go rancid, antioxidants are ineffective, or sunscreens break down and don’t protect as well. The other aspect, preventing bacterial growth, is important because after the expiration date, there is no guarantee the product is still sanitary and safe. Even if it looks normal and smells okay, it can still have germs growing in it. So what’s the consensus? After the expiration date, your active ingredients will not work as well and there can be bacteria brewing inside. I’d recommend tossing it!