Allergies have become widespread in developed countries. The reason? Excessive cleanliness is to blame,” said Dr. Guy Delespesse, an immunologist and director of the Allergy Research Laboratory at the University of Montreal. While family history, air pollution, processed foods, stress and other factors can trigger allergic reactions, Dr. Delespesse is concerned by “our limited exposure to bacteria” .
The idea that too-clean environments contribute to allergies is called the “hygiene hypothesis.”
The study suggest that exposure to germs and infection helps build the immune system, which can protect against allergies and asthma. The explanation is simple: we are so hygienic we aren’t being exposed to the same level or variety of bacteria as in the past, so our immune systems are unable to build up defences.
There is an inverse relationship between the level of hygiene and the incidence of allergies and autoimmune diseases,” said Dr. Delespesse. “The more sterile the environment a child lives in, the higher the risk he or she will develop allergies or an immune problem in their lifetime. Some 50 million Americans suffer from allergic conditions and about 15 million Americans have asthma, and the numbers are increasing, according to the AmericanAcademy of Allergy, Asthma and Immunology. The cost of treating allergies and asthma stands at about $32 billion a year. And there is much misery: 60 percent of allergy sufferers say they were unable to find ways to stamp out the seasonal ills, according to a survey released this week by ConsumerReportsNationalResearchCenter. Dr. Delespesse also frets about the burgeoning allergic population. He noted that 10 percent of people in developed countries suffered from allergies two decades ago. Today, the percentage has increased threefold to 30 percent, with one in 10 children suffering from asthma. Deaths from that condition are also increasing, he said.
Allergies rose rapidly in developing nations where living conditions and hygiene standards were becoming more like those in the West.
Cleanliness does reduce our exposure to harmful bacteria. As the human immune system matures, normally it learns how to differentiate what is not dangerous from what is dangerous. If you raise children in too clean of an environment, this distinction is missing.” If infants encounter a wide range of bacteria they are less at risk of developing allergic disease later in life. This is the conclusion of research from the University of Copenhagen, which suggests completely new factors in many modern lifestyle diseases.
“In our study of over 400 children we observed a direct link between the number of different bacteria in their rectums and the risk of development of allergic disease later in life,” says professor Hans Bisgaard, consultant at Gentofte Hospital, head of the Copenhagen Prospective Studies on Asthma in Childhood, and professor of children’s diseases at the Faculty of Health Sciences, University of Copenhagen.
Reduced diversity of the intestinal microbiote during infancy was associated with increased risk of allergic disease at school age. But if there was considerable diversity, the risk was reduced, and the greater the variation, the lower the risk. When the immune system not constantly battling dangerous bacteria, “it doesn’t know what to fight against,”
“So it makes a difference if the baby is born vaginally, encountering the first bacteria from its mother’s rectum, or by caesarean section, which exposes the new-born baby to a completely different, reduced variety of bacteria. This may be why far more children born by caesarean section develop allergies.” said Professor Bisgaard.
In the womb and during the first six months of life, the mother’s immune defenses protect the infant. Bacteria flora in infants are therefore probably affected by any antibiotics the mother has taken and any artificial substances she has been exposed to.
“We have studied staphylococci and coli bacteria thoroughly, and there is no relation. What matters is to encounter a large number of different bacteria early in life when the immune system is developing and ‘learning’. The window during which the infant is immunologically immature and can be influenced by bacteria is brief, and closes a few months after birth.
“I must emphasize that there is not one single allergy bacteria,” Professor Bisgaard points out. “I think that a mechanism that affects the immune system will affect more than just allergies, he concludes. It would surprise me if diseases such as obesity and diabetes are not also laid down very early in life and depend on how our immune defenses are primed by encountering the bacterial cultures surrounding us.”