Psoriasis versus Scabies

I have been suffering for some months with a skin lesion on my wrist which appears to have originated with some unknown bite or sting. That then caused a general swellling in the arm requiring anti-biotic treatment.That was successful at the time (some months ago) but the bite/sting area remained visible but inactive. Recently the arm area began to have red blotches which expanded to cover much of my skin area each becoming irritable and producing a scratchy area with a surface roughness and areas of dead skin 'plaques'.. The GP examined this (no skin sample taken) and decided it was Scabies - the result of tiny burrowing insects. Permethrin cream was prescribed but the condition is unchanged. Is this perhaps Psoriasis?