The double-blinded and placebo controlled study, led by researchers at the UK's Institute of Food Research (IFR) found that taking a the probiotic drink led to alterations in how cells lining the nasal passages of hay fever sufferers reacted to a single out-of-season challenge.
However the team led by Kamal Ivory at the IFR noted that consumption of the Lactobacillus casei Shirota (LcS) probiotic strain did not lead to significant changes in total hay fever symptoms - the primary clinical endpoint of the study.
"Daily oral supplementation with LcS modified some parameters of allergic inflammation at the nasal mucosa but this was not paralleled by significant changes of clinical symptoms of seasonal allergic rhinitis," revealed the authors, writing in PLoS One.
Ivory and colleagues noted that an absence of 'overt clinical benefit' may be due to an inability of single nasal challenges to accurately represent natural allergen exposure, and noted that oral delivery of the probiotic strain did produce changes in the immunological microenvironment at the nasal mucosa.
The research team gave 60 hay fever sufferers daily drinks for 16 weeks, outside of the hay fever season. One group was given a drink containing Lactobacillus casei Shirota, and the other group received very similar drinks without the probiotic. The study was double-blinded and placebo controlled.
Samples were taken from the volunteers' nasal cavities and blood, both before and after being challenged with pollen to trigger their allergy, explained the team. This was done at baseline and repeated at the end of the 16-week intervention.
Volunteers who received the probiotic drink saw changes in allergic inflammation in their nasal lining, as well as changes in their blood, that are associated with immune responses.
Ivory and her colleagues said their findings provide strong evidence of how the gut microbiota can influence cells of the gut lining, and have a systematic influence on our bodies and distant cells, such as those lining our nasal passages.
But noted that despite this, the probiotic had no detectable effect on the symptoms of hay fever.
The IFR researchers used a single allergy challenge, applied to the volunteers' nasal passage, to provide a standard, reproducible test to help ensure all the subsequent results are comparable. However the team suggested that in the real world hay fever is usually triggered by longer term exposure to the allergen, variable in strength and timing over a period of days or weeks.
Therefore the team are now exploring the possibility of carrying out a seasonal study to investigate whether the changes in the nasal mucosa seen in this single challenge study relate to changes in hay fever symptoms triggered by a more realistic natural exposure to pollen.
Source: PLoS One
Published online ahead of print, doi: 10.1371/journal.pone.0078650
"Oral Delivery of a Probiotic Induced Changes at the Nasal Mucosa of Seasonal Allergic Rhinitis Subjects after Local Allergen Challenge: A Randomised Clinical Trial"
Authors: Kamal Ivory, Andrew M. Wilson, et al