Upper respiratory tract infections (URTIs) are illnesses caused by an infection of mucosal surfaces in the nose, sinuses, pharynx and/or larynx. These infections include the common cold, rhinosinusitis, tonsillitis and otitis media and are very common, especially among infants, children and elderly. URTIs are among the most common reasons for people to visit their doctor and they account for a large part of antibiotic use in high-income countries. Although antibiotics are very effective in clearing infections, they come with negative side-effects such as antibiotic resistance. This has prompted researchers to look into more natural alternatives, such as probiotics, for treatment and/or prevention of URTIs. Mechanisms by which probiotics may be effective are thought to be related to restoration of the microbial balance in the upper respiratory tract and stimulation of the immune response. Based on these scientific insights the probiotic formulation, Winclove 381 Respiratory, to prevent URTIs was developed.