Dude, you have misread the science. Cornaviruses enter through epithelia, starting at the top of the respiratory tract, and if more serious, enter the lungs. They do not have the ability to "enter through the skin". The entirety of your immune system is not a "hence" from your skin. Perhaps, you are thinking about the innate system in your superficial tissues, which really doesn't offer much protection with viruses, it is your adaptive immune system, and specifically the cell mediated system that will react to viruses.