15 Feb 2016
These days it seems that everyone at least knows of someone with an allergy, if not suffer with one themselves. Allergies have become increasingly prevalent in the UK. Allergy UK estimate that approximately 18 million people suffer with hay fever and the numbers are rising every year. In fact, allergies are widely regarded by the scientific community as a 'Western' disease, being that they are far more common in developed countries in comparison to the developing world.
This is thought to be a consequence of the diet, lifestyle and environment which has become common in western societies. A diet consisting of processed foods, coupled with stressful lifestyles and with no or little contact with a natural environment limits our exposure to naturally occurring bacteria, and is thought to be a major contributing factor to the rise in allergies. Scientists believe that this combination of factors may impact the diversity of our microbiome as well as our immune systems. This idea has been coined as the 'hygiene hypothesis', which we've discussed frequently here on our blog.
Now a new study1 of 1,879 American adults has found further evidence to support the hypothesis. Researchers from the American National Institutes of Health sought to find out why an altered gut microbiota may increase the risk of developing allergies and other conditions. They analysed questionnaires from participants, which asked them to self-report their history of allergies, as well as faecal samples from each individual.
The researchers found that out of the 1,879 participants, 81.5% reported to have one or more allergies. This ranged from just 2.5% having a peanut allergy to 40.5% self-reporting a seasonal allergy such as hay fever. They compared questionnaire results with faecal sample results and found that those with allergies had less diversity in their gut bacteria. In fact, the more allergies an individual had the less diversity they observed in their gut bacteria.
Of single allergies, gut microbiota diversity was lowest in those with hay fever or peanut allergies. The scientists were able to identify that these individuals had lower levels of Clostridiales bacteria, and increased levels of Bacteroidales. The researchers concluded that gut microbiota intervention through the potential use of probiotics may help in the treatment or prevention of such allergies. Further research is needed to further understand the role of the gut microbiota in relation to allergies.
Other research in this area has found that probiotics may be helpful in preventing hay fever, especially when taken prior to the hay fever season. In fact, certain strains may help alleviate nasal irritation in sufferers of birch tree pollen allergy.
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1. Xing, H. et al. (2015) Allergy association with the adult fecal microbiota: Analysis of the American Gut Project. Elsevier. Published online ahead of print, 27 November 2015.