Scientists from Karolinska Institute have refuted the hypothesis that very good hygiene and the “lack” of microbes in the environment lead to the development of allergies. The research was published in the journal Science Immunology.
The idea that adequate microbial exposure may reduce the risk of developing allergies has emerged in the last few decades and has been called the hygiene hypothesis. Research has confirmed that some infections can reduce the production of inflammatory antibodies to allergens.
To test the hygiene hypothesis, scientists conducted an experiment on mice. They compared the allergic immune response in “dirty” wild and “clean” laboratory mice. The mice were genetically identical, but wild-type mice were kept in semi-natural conditions and exposed to heavy microbial exposure from birth. Biologists found no evidence for the hygiene hypothesis. In contrast, wild mice developed even more pronounced signs of pathological inflammation and allergic reactions when exposed to allergens.
The findings may have implications for medical research. Attempts are being made in clinical trials to treat patients with inflammatory diseases through worm infection or fecal transplantation (transplanting the gut microbiota from a healthy person to a sick person). Scientists’ work will allow us to better understand the potential of such interventions.
The authors believe that the hygiene hypothesis may be true in some cases, but their study showed that this is not a general rule.
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