Although there have been many studies on the effect of probiotics on allergy symptoms, so far, the data have been inadequate to be conclusive. Here's another study that suggests that a daily dose of Yakult, a probiotic drink originally developed in Japan, can change the IgE levels in people with hay fever.

In this study, volunteers with a history of seasonal hay fever drank a daily milk drink with or without live bacteria over 5 months.

The probiotic drinks contained Lactobacillus casei, a bacterial species that has been widely studied for its health promoting properties.

Blood samples were taken before the grass pollen season, then again when it was at its peak (June), and 4 weeks after the end of season.

There were no significant differences in levels of IgE in the blood between the two groups at the start of the study, but IgE levels were lower in the probiotic group both at the peak season and afterwards.

At the same times, levels of the antibody IgG were higher, a type of antibody that in contrast to IgE is thought to play a protective role against allergic reactions.

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

the manifestation of symptoms, however, were not observed, so it still is unknown whether the immune system changes actually translates to reduced allergic reactions. Also, the study was conducted with only a small number of patients, so a larger scale study still needs to be conducted.