Vitamin C does not prevent the common cold but may decrease the severity and duration of symptoms. Vitamin D may decrease the incidence of influenza and other viral infections as well as tuberculosis. Zinc does not prevent the common cold but also decreases severity and duration of symptoms. Probiotics do not prevent respiratory infections but may decrease severity and duration of symptoms. Xylitol decreases the risk of ear infections by 32%. Garlic may decrease the risk of the common cold, but the evidence comes from one study.