There are a few things you can do to prevent getting a rash on your face after you shave. First, make sure that the razor you are using is sharp and clean. A dull razor or one that is full of bacteria can cause a lot of irritation to your skin. Second, use a shaving cream to help lubricate your skin and protect it from the razor. Third, shave in the direction of hair growth to avoid irritation. And finally, rinse your face with cool water after shaving to soothe any irritation. And finally, use antiseptic products like witch hazel and alum blocks to clean your pores.