The study is published on Friday i Science Immunology. It is researchers at the Karolinska Institute who compared mice, which from birth were exposed to possible infections, with “clean” laboratory mice that escaped living with viruses, bacteria, molds and yeasts.
It shows that the mice raised with microbes under dirty conditions run the same, or even greater, risk of developing allergic immune responses than the “clean” mice.
No general rule
Jonathan Coquet, docent in microbiology at the Karolinska Institutet, thinks the result is a bit unexpected:
– It suggests that it is not as simple as saying “dirty lifestyles will stop allergies while a clean lifestyle can trigger them”.
He believes that there are specific contexts where the hygiene hypothesis is true, but believes that perhaps it should not be considered a general rule.
In recent years, attempts have been made to treat certain inflammatory diseases by, for example, exposing patients to parasitic worms or transplanting foreign feces into the intestine. Clinical experiments aimed at causing the induced infection to cause the body to react and start fighting the actual disease.
The hopes for future treatment methods are high. What the researchers behind the animal study want to point out is that close contact with microbes may not have the positive effects that many desire. At least not always.
Excessive fear of germs
Agnes Wold, professor of clinical bacteriology at Sahgrenska, has long been at the forefront of the fight against what she considers excessive fear of germs and cleanliness mania.
She has not had the opportunity to read the study, but writes in a text message that experiments on mice do not say much about humans, because the immune systems work differently.
– There is as much evidence as possible from humans that a clean upbringing with few microorganisms is associated with a higher risk of allergy, autoimmune diseases and inflammatory bowel disease.