Rash from 39-year old US male diagnosed with chronic blastocystosis acquired domestically. Skin rash in Blastocystis infection has been described as recurrent  and intensely pruritic . Diagnosis of blastocystosis was by exclusion: eleven ova and parasite exams (trichrome staining) performed at clinical laboratories from 2003–2006 were negative except for findings of Blastocystis. Colonoscopy, endoscopy, and gluten challenge test were negative. The infection was unresponsive to metronidazole, nitazoxanide, and TMP/SMX. The isolate was genotyped as Blastocystis sp. subtype 3 in a 2007 study .