The team, from New York University, analysed data from 7,412 children and young people. Those aged 3 to 19 were 25% less likely to have asthma if they were carriers of Helicobacter pylori. Those aged 3 to 13 were 59% less likely to have asthma if they carried the bacteria than those that didn’t.
Whilst asthma and other conditions linked to allergens have been increasing in recent years, H. pylori has been disappearing from the guts of humans in developed countries. High use of antibiotics, cleaner water and homes have contributed to this.
In the study, only 5.4% of children born in the 1990s were positive for the bacteria and 11.3% of those under 10 had taken an antibiotic in the month before.
Dr Martin Blaser, professor of internal medicine, hypothesized that the difference could be to do with the different immunological status of carriers and non-carriers.
‘If you have Helicobacter you have a greater population of regulatory T-cells that are setting a higher threshold for sensitization.
‘So if a child doesn’t have Helicobacter and has contact with two or three cockroaches, he may get sensitized to them. But if Helicobacter is directing the immune response, then even if a child comes into contact with many cockroaches he may not get sensitized because his immune system is more tolerant.’