Oh twiglett so sorry for you - I know what you are going through with the dread, every time dd has diarrhoea I wonder if this is the onset of Crohn's and if she has inherited it from me :(
How about the chinese herbal route? My MIL had terrible psoriasis which was totally cured that way and so was my eczema.
Could it be impetigo or something like that - I would see a GP just on the basis that it could easily be something else and that would then remove your immediate worry that ds has the psoriasis.
Big hugs to you ((()))