�Good� bacterial content in a daily drink can change the immune system�s response to grass pollen, balancing antibodies in a way that may provide relief to those who suffer hayfever allergies, according to a study.

"Good" bacterial content in a daily drink can change the immune system's response to grass pollen, balancing antibodies in a way that may provide relief to those who suffer hayfever allergies, according to a study.

"Probiotic supplements modulate immune responses and may have the potential to alleviate the severity of symptoms," said researchers at the Institute of Food Research, Norwich, in the journal Clinical and Experimental Allergy, though they cautioned that further research was needed.

Probiotics contain live micro-organisms - so-called "good bacteria" - that colonise the intestine. They are sold as supplements but are also found naturally in many fermented foods including yogurt and certain juices. Humans normally carry several pounds of bacteria in their intestines. They are key to digestion and immune-system function and possibly play other beneficial roles. They can also out-compete "bad" bacteria that may cause disease.

In the study, volunteers with a history of seasonal allergies drank a daily milk drink with or without Lactobacillus casei - a bacterium widely studied for its beneficial properties - over a five-month period. Researchers took blood samples before the grass pollen season, at its peak and afterwards. They found that people who had been drinking the probiotic had lower levels of an antibody that helps produce allergy symptoms. At the same time, these people had higher levels of the antibody IgG, which may play a protective role against allergic reactions.