Masking while you sleep is an excellent way to moisturize your skin during dry, cold winter months. But before trying out this masking trend, there are a couple of things you should keep in mind. First, overnight and regular masks are not the same, and you shouldn't use them interchangeably. The difference between sleep masks and other masks is that traditional masks are not designed to be worn overnight and may have ingredients that shouldn't be left on your skin long-term. Secondly, you should remove overnight masks in the morning by cleansing your face. Beauty experts and dermatologists say that leaving them on can increase the risk of breakouts, especially if you are acne-prone.