Probiotics are nonpathogenic microorganisms that, when ingested, exert a positive influence on the health or physiology of the host. More than 20 microorganisms have this property and therapeutic effects on nearly 10 diseases. Even though they have less side effects when compared to antibiotics, it is still necessary to be aware of which strains are efficacious in different diseases, and the optimal composition, dosage, and length of treatment for each clinical setting must be determined.