The common cold is a viral infection primarily caused by rhinoviruses.  Previous studies have shown that probiotics, alone or in combination with prebiotics, have reduced the incidence of upper respiratory tract infections. Swedish researchers enrolled 272 men and women in a 12-week long study, during which subjects were supplemented daily with supplemented either with 109 cfu (colony forming units) of probiotics or placebo.  The team found that the probiotics reduced the incidence of one or more episodes of the common cold. Among those who received the probiotics, both the total symptom score and number of symptom days among were markedly reduced. The researchers conclude that:  “Intake of the probiotic strains Lactobacillus plantarum and Lactobacillus paracasei reduces the risk of acquiring common cold infections.”