Your skin protects you from a multitude of dangerous things that exist from the environment. Bacteria, viruses, UV light, and more is prevented from entering your body and harming your inner organs thanks to the protective action of your skin.
It isn't just the outer layer of your skin that you can see that protects the body. The skin is made up of multiple layers that each perform different actions to keep pathogens out and clear them out if they break through the barrier. Listen to Dr. Mark Coles from the University of York talk in more detail about the skin and its role in preventing acne.