<s>[INST] After waking about 12 miles yesterday a red rash has appeared on my lowers legs. I was wearing long trousers and gaiters.  I walked again to day about the same distance and the rash is about the same.  This has happened occasionally for the past 20 years and it disappears after a day or so. Some people refer t it asw hikers rash. [/INST] Its a form of small vessel vasculitis. Confirmation of diagnosis is by skin biopsy and H& E staining as well as by Immunoflorescence </s>