Birch pollen allergy is one of the most common forms of respiratory allergy in the Nordic countries. Treatment consists of antihistamine use. Specific probiotic strains have been observed to modulate the immune system. Since the body has a common mucosal immune system; it was hypothesised that consumption of probiotics may affect also the respiratory mucosal immune response and hence affect respiratory allergy.

Earlier studies with probiotics had been unable to show improvements in adults with pollen allergy. It was therefore hypothesised that children, who's immune system is not yet fully developed, might be better targets.