Urticaria by Blastocystis hominis. Successful treatment with paromomycin

Urticaria and angioedema are easily recognized disorders, but in at least 70 percent of individuals, chronic episodes of urticaria are of unknown causes. We present 10 cases of chronic urticaria associated parasitation by blastocystis hominis. This parasite has not been previously related with urticaria. Both intestinal parasitation as well as urticaria responded successfully to paromomycin sulfate.