MedWire News: People with hayfever may benefit from taking daily doses of 'good' bacteria, called probiotics, to reduce symptoms of the condition, researchers have found.

Hayfever, which is also called allergic rhinitis, is an allergic reaction to pollen and other environmental allergens. The immune systems of people with the condition mistake pollen for harmful substances and produce excess amounts of an antibody called immunoglobulin E. This results in symptoms such as watery eyes, sneezing and a runny nose.

Changes in the composition of gut bacteria have been implicated in the development of allergic disorders, "suggesting beneficial interactions between the intestinal immune system and specific bacterial strains", explain lead researcher Dr Kamal Ivory and colleagues from the Institute of Food Research in Norwich, UK.

The researchers investigated whether a type of 'good' bacteria called Lactobacillus casei Shirota could help reduce symptoms in people with hayfever.

The team studied 10 patients with the allergic condition who were asked to drink milk with or without Lactobacillus casei Shirota every day for 5 months.

Blood samples were taken from the participants before, during and after the grass pollen season and tested for levels of immunoglobulin E. These blood samples were also tested for levels of another antibody called immunoglobin G, which is thought to play a protective role against allergic reactions.

The researchers found that there were no significant differences in levels of immunoglobulin E between the two groups at the start of the study. However, during and after the grass pollen season, participants taking Lactobacillus casei Shirota had significantly lower levels of this antibody than those who were not taking the probiotic.

Correspondingly, levels of immunoglobin G were significantly higher in the probiotic group during and after the pollen season than in the other group.

"The probiotic strain we tested changed the way the body's immune cells respond to grass pollen, restoring a more balanced immune response," said Dr Kamal Ivory.

Writing in the journal Clinical and Experimental Allergy, Dr Kamal and team conclude: "These data show that probiotic supplementation modulates immune responses in allergic rhinitis and may have the potential to alleviate the severity of symptoms."