Hygiene Hypothesis

This hypothesis, which is supported when looking at many parasitic infections, is based on the finding that parasites may influence intensively the immune system of their host by stimulation of its activity. Thus it was concluded that the diseases of our modern times such as Crohn syndrome, allergies, autoimmunity effects, metabolic syndrome, etc. are consequences of the strongly and constantly diminished exposure to infectious agents of diseases in our days in Europe and USA. In consequence, it becomes intelligible that artificial exposure of humans to pathogens (e.g., infections of humans with Trichuris suis ) reduces symptoms due to autoimmune diseases such as Crohn syndrome or ulceritis.