But a surprising new study suggests that exposure to cat dander, a wide variety of household bacteria – and even rodent and cockroach allergens – can help protect infants against future allergies and wheezing..
Interestingly, contact with bacteria and dandruff after 1 year of age was not protective – it actually increases the risk. “It was the opposite of what we expected,” said Dr. Robert Wood, chief of the division of allergy and immunology at Johns Hopkins Children’s Center and co-author of the study in the Journal of Allergy and Clinical Immunology. “We are promoting bringing rodents and cockroaches in the house, but this data suggests that being too clean can not be good.”
The new findings could help explain some inconsistencies in research on so-called hygiene hypothesis, which suggested that children who grow up in a super clean environment were more likely to develop allergies.
“This is not completely solve the dispute, but adds a large piece of the puzzle,” said Dr. Jonathan Spergel, professor of pediatrics and chief of allergy at the Children’s Hospital of Philadelphia.
The hygiene hypothesis was developed after the researchers noted that farm kids were less likely to have allergies. Dirty environments, experts suggested, may have a protective effect. The hypothesis seemed to explain why developed countries had triggered the rates of allergies and asthma.
“We are promoting bringing rodents and cockroaches in the house, but this data suggests that being too clean can not be good.”
The theory “is that as we clean up our environment, our immune system is oriented away towards the fight against bacteria and parasites,” said Dr. Maria Garcia Lloret, assistant clinical professor of pediatric allergy and immunology at the Hospital Mattel children at the University of California, Los Angeles. “So it has nothing to do and starts reacting against things that are generally harmless, such as dust mites or cat dander or cockroaches or peanuts.”
A crack in the hygiene hypothesis seemed to be the high rates of allergy and asthma in environments city center. But the new study may help explain the contradictions, showing that early exposure is crucial.
“It’s all about exposure to the right people at the right time bacteria,” Spergel said.
Wood and colleagues followed 467 infants for three years, selecting them for allergies a year and test house dust allergens and bacteria where they lived. To the surprise of researchers, children who were exposed before their first birthday mouse and cat dander with cockroach droppings had lower rates of allergies and wheezing at 3 years compared with those who were not exposed so early .
In fact, wheezing was three times more common among children with less exposure to allergens early in life.
The protective effect of early exposure to allergens is amplified if the house also contained a wide variety of bacteria.
The reason may be that “much of the development of the immune system that can take someone down the road of allergies and asthma can be ruled early in life,” Wood said.
Researchers are not willing to try to translate new findings into practical advice for parents. But Lloret said, we now know that the “strict avoidance of allergens from the beginning does not protect, and early exposure in context can make the difference between illness and tolerance. You could say that this is the downside of cleaning “.
The new findings could put head experts have been giving advice to parents about pets and babies.
“Twenty years I used to say to parents for cats and dogs in the household ago,” Wood said. “This shows that the younger a child is when you get a pet, the better.”