If I do this am I committing a skincare sin? I’ve used moisturiser all my life but recently started using serum. The thought occurred to me other day that my make up might stay on better if I just used serum instead of moisturiser rather than as well as. It worked ok but I’m wondering if I continue to do this will my skin suffer? I’m the opposite of a skincare expert and I find it all a bit baffling so any advice appreciated