 The prevalence of allergic and autoimmune diseases is increasing in developed countries, possibly due to reduced exposure to microorganisms in childhood, hygiene hypothesis. Epidemiological and experimental evidence in support of this hypothesis is accumulating. In this context, parasitic helmets are now important candidates for anti-allergic anti-inflammatory agents. Here we summarize anti-allergic, anti-inflammatory effects of helmets together along with our own study of the effects of schistosoma mansoni on TH-17, dependent experimental arthritis. We also discuss possible mechanisms of helmet-induced suppression according to the recent advances of immunology. This article was authored by Yoshio Osada and Tomotsu Konozawa.