A child’s risk of developing asthma is the smaller the more the microbiota of the child’s home resembles that of a farm house. This was shown by a study conducted by the Finnish National Institute for Health and Welfare (THL) that analysed indoor microbiota from 400 Finnish and 1,000 German homes.
Studies show that allergies are on the rise in developed countries, including the United States — not just seasonal allergies, but allergies of all kinds.
Rodent studies have revealed that the composition of gut microbiota and its remodelling is associated with different diseases, such as Parkinson’s disease, depression and autism spectrum disorders, but little research has been conducted on infants and children.
The hygiene hypothesis holds that, when babies’ exposure to germs is so limited, their immune systems are deprived of the opportunity to learn how to fend off pathogens properly…consequently their immune systems become so sensitive that the babies develop allergies.
Earlier research has shown that growing up on a farm with animals may as much as half the risk of asthma and allergies. The protective effect is thought to be attributable to the diverse microbial exposures encountered on farms.
“We now discovered that the presence of farm-like microbiota in an early-life home seemed to protect from asthma also in urban homes. The effect was not based on the presence of large number of different microbial species but, rather, differences in the relative abundance of certain bacterial groups,” says Pirkka Kirjavainen, Senior Researcher at THL.
Wearing Outdoor Shoes Indoors, The Number of Siblings and the Age of the House Play a Role
The study found that the microbiota in homes protecting from asthma contained a wealth of bacteria typical of the outdoor environment, including bacteria in soil. On the other hand, the proportion of microbes normally occurring in the human respiratory tract and associated with respiratory tract infections was small.
“The key characteristic of microbiota in homes protecting from asthma appears to be large abundance of bacteria which originate from the outdoor environment and are beneficial or harmless to health, relative to bacteria that are a potential threat to our health,” Kirjavainen comments.
In urban homes, factors that increased the farm-like features in the microbiota included wearing outdoor shoes indoors, the number of siblings and the age of the house; all factors that may increase transport ofoutdoor microbes into the home.