Exposure to a wide range of bacteria is necessary to prime the immune system early in life, according to the hygiene hypothesis . Western diets and an emphasis on sterile, germ-free food has made us more likely to allergies, new research suggests. A lack of bacteria in the gut means we are less equipped to deal with germs - meaning that our bodies often overreact when we come into contact with bugs, dust or pollen. The findings bolster the theory that modern obsession with hygiene and cleanliness has driven a boom in allergies and health problems. According to the ‘hygiene hypothesis’, exposure to a wide range of bacteria is necessary to prime the immune system early in life. Many scientists believe that modern society, with its mania for sanitation and easy access to antibiotics, makes us hypersensitive to harmless allergens. The latest work, published today in the journal Cell Reports, compared the bacteria in the guts of people from the US and Papua New Guinea - one of the least industrialised nations on Earth. The research, by Canadian and Australian scientists, found that people in the US had far smaller collection of bacteria - called the ‘microbiome’ - than people from Papua New Guinea. Study author Jens Walter, of the University of Alberta in Canada, said: ‘There are several aspects of western lifestyle that have been hypothesized to alter the gut microbiome and decrease diversity. ‘These include diet, sanitation, and clinical practices such as antibiotic use and caesarean sections, but we lack a conceptual understanding of how our microbiomes are altered.’ The research team found that Papua New Guineans have vastly different compositional profiles compared with US residents. Americans lacked 50 different bacterial types present in most Papua New Guineans. Professor Walter said: ‘These findings suggest that lifestyle practices that reduce bacterial dispersal - specifically sanitation and drinking water treatment - might be an important cause of microbiome alterations. ‘We propose a model based on ecological theory that fits the data and provides an explanation for the decline of microbiota diversity in urban-industrialized societies.’ The scientists insisted that treating food and water is still vital - reducing the number of illnesses and deaths from bacterial infections. A lack of bacteria in the gut means we are less equipped to deal with germs - meaning that our bodies often overreact when we come into contact with bugs, dust or pollen (file photo) But they said that Western diets may have contributed to increases in some chronic diseases. Asthma, peanut allergies and hayfever are examples of allergic conditions that have been linked by previous research to the problems caused by insufficient bacteria in the gut. Co-author Andrew Greenhill, a senior lecturer in microbiology at Federation University Australia, said: ‘We can think about how we can reduce the collateral damage of modern lifestyle practices on the gut microbiome without jeopardizing the benefits. ‘The findings from this study provide information that could be used to develop strategies to prevent and redress the impact of westernization and potentially support the dispersal and transmission of microbes that have been eradicated.’ The more bleach used in the home, the more likely children were to become ill, a study found . Bleach could leave children more susceptible to catching flu, tonsillitis or other infections, according to a study published earlier this month. Researchers found a link between a weekly use of bleach in the home and the frequency of infections, particularly respiratory ones. They concluded that passive exposure to bleach was associated with a 20 per cent increase in the risk of flu in the previous year. It was also linked with a 35 per cent rise in the risk of recurrent tonsillitis. In light of the findings, experts said the use of bleach in the home was a 'public health concern.' The study looked at the potential impact of exposure to bleach among more than 9,000 schoolchildren between the ages of six and 12 in the Netherlands, Finland and Barcelona. Parents were asked to complete a questionnaire on the number and frequency of flu, tonsillitis, sinusitis, bronchitis, otitis (inflammation of the ear canal), and pneumonia infections their children had suffered in the preceding 12 months. They were also asked whether they used bleach to clean their homes at least once a week. The study took into account factors such as passive smoking at home, parental education, household mould and use of bleach to clean schools. The findings indicated that the number and frequency of infections were higher among children whose parents regularly used bleach to clean the home in all three countries. As well as being statistically significant for flu and tonsillitis, the risk of any recurrent infection was 18 per cent higher among children whose parents regularly used bleach. One possible explanation was that the irritant properties of compounds generated during the cleaning process may damage the lining of lung cells, sparking inflammation and making it easier for infections to take hold.
Lack of bacteria in the gut means we are less equipped to deal with germs . Means our bodies overreact when in contact with bugs, dust or pollen . Study: People in the US had far smaller collection of bacteria - called the 'microbiome' - than people from less sanitised Papua New Guinea .