A recent study on children attending day care or nurseries by de Jongste in the American Thoracic Society journal cast some doubt on the so-called Hygiene Hypothesis for allergy development. The Hygiene Hypothesis notion that farm animal faeces exposure and childhood infections will prevent allergies has been promoted for decades. The hygiene hypothesis essentially links a more clean and sterile home environment with the overall rise in allergies seen in many developed Western counties. Poor living conditions with early exposure to germs, infections and parasites seem to shift the infant’s immune system into survival mode (TH1) and away from allergy mode (TH2) when allergy testing. However this immune switching probably occurs very early in the first few months of life. Therefore as mentioned in the American study, day care centre exposure and subsequent childhood infections may have little impact on allergy development. Particularly if the child attends a day-centre after one year of age when their immune type reactivity is more established. It still seems likely that a germ-filled household with difficult living conditions and plenty of sickly older siblings will be more protective from allergies while a sterile, insular environment in early infancy seems to promote allergies.
Posts Tagged ‘parasite’
Home hygiene, infections and allergies
Thursday, November 12th, 2009Can worms prevent allergies?
Saturday, October 17th, 2009The 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
