The current epidemic of allergic disease seems to be in part related to living in a much cleaner more sterile environment together with a lack of parasitic worm infestations. This leads to an early switch in the infant’s immune systems to reacting in a more allergy prone (TH2) manner and less of a bacteria and viruses (TH1) targeting manner.
In a recent study published in Clinical and Experimental Allergy, investigators found that if mice had their gut infested with parasitic worms, they developed fewer food and airway allergies, but the parasites gave no protection from skin allergies. This is the first evidence that intestinal worms can actually modulate the immune system and “protect” against developing allergies.
A similar study on Vietnamese children showed that if they were treated to eradicate their parasitic gut hookworms, they became much more likely to develop house dust mite allergies and asthma.
Reference: Gastrointestinal nematode infection interferes with experimental allergic airway inflammation but not atopic dermatitis. Hartmann S, Schnoeller C, Dahten A et al. Clin Exp Allergy 2009 (39) 1585-1596.
http://news.bbc.co.uk/2/hi/health/8268584.stm
