I completely agree with what artful_lounger says. It's great that you are keen to explore a career in dermatology, but please be mindful that a medical degree is required and it will be many years before you start and graduate before you will be solely focusing on Dermatology. It is a very competitive speciality and there a few trainee positions, but these considerations are not essential at your stage.
I think it would be worthwhile you reflecting on what it is about dermatology you are interested in, therefore you can tailor your choice of applications accordingly. You can only apply to four medical schools as part of UCAS so you fifth (and final choice) could be something related you want to consider.
I would recommend looking further into the Chemistry pharmaceutical route as you mentioned as well as Aesthetics.
Hope this is useful!