Kids can be too clean

Kids can be too clean

Scientists are studying the potential link between lack of exposure to bugs in childhood and later development of allergies or diseases such as type 1 diabetes

Are allergies and so-called autoimmune diseases, like type 1 diabetes, likely to be caused by a lack of exposure to relatively benign pathogens in early childhood? This theory is referred to as the hygiene hypothesis. If proven true, better insight in the processes at work could lead to better prevention or treatment. A new study called Diabimmune, funded by the EU, precisely aims to shed additional light on the hygiene hypothesis, by the time it is completed in 2015.

The project focuses on a very unique location at the border region between Finland, Estonia and Russian Karelia. “It’s a scientists dream,” says project coordinator Mikael Knip, professor of pediatrics and chief physician at the University of Helsinki Children’s Hospital, in Finland. “Here we have three populations with virtually the same genetic susceptibility for diabetes type 1 and allergies. But in Finland they occur seven times more often than in the much poorer region of Karelia. And Estonia is a country in rapid development where we can see the change happening.” All in all, 4,500 subjects spread between two groups—namely infants up to 3 months old and children between the age of 3 and 5 years old—take part to the study. These were also equally split between the three countries.

The setup of the project study is exemplary, some believe. “This triplet-nation study can indeed provide us with much needed extra information,” says Maria Yazdanbakhsh, head of the department of parasitology at Leiden University, in the Netherlands. She was previously involved in research amongst children in Africa, who were all permanently infected with intestinal worms, yet did not develop the corresponding allergy to helminth parasites. Her work proved the validity of the hygiene hypothesis further. But her team has not been able to identify the protection mechanism.

Other experts in the field believe it may not be neccessary to extend the scope of the study to children between 3 and 5 year old. “I’d focus first and foremost on infants up to the age of 3 months,” comments Edwin Gale, emeritus professor and expert in the epidemiology of type 1 diabetes at the University of Bristol, in the UK. He believes that the first three months of their life is the time when a child should normally get in contact with pathogens. “It’s also the period wherein its immune system learns to react forcefully, without running amok, that would cause allergies, and without attacking its own body, like it does in the case of diabetes type 1,” he tells He adds: “I wouldn’t bother too much with children of [between] 3 and 5 years old.” 

He sees the benefit of an early exposure to pathogens. However, it should be done in a measured manner. “Of course, we shouldn’t return to former poor standards of hygiene,” he says, “It’s idiotic to think I suggest getting our babies dirty on purpose.” If we fully understand how the immune response works, Gale believes, we might be able to develop harmless pathogens —for instance in a pill, or a liquid—that will teach the immune system to behave, and do nothing else. 

Yazdanbakhsh agrees: “If we do this in a controlled way, certain benign pathogens can be given to infants [to] help them develop a sturdy immune system.” She refers to the example of worm therapy, currently being tested. “The first results are very promising,” she adds.

One question remaining is whether the project is likely to prove the hygiene hypothesis. Knip concludes: “That’s too early to say for certain. Preliminary results however point strongly in that direction. And I believe probiotics—stronger ones than we have today—could play an important role in reducing allergy and type1 diabetes in highly developed countries.

But for now, Knip concludes: “I’d advise expecting parents to get a pet before the first child is born. I’m sure it’ll help.”

Image credits to: Sean Dreilinger

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