Probiotics are useful for -
Probiotics are substances secreted by one organism which stimulates the growth of another.

Probiotics are useful in following conditions:

Rota virus diarrhea
Antibiotic associated diarrhea
Radiation induced diarrhea
Traveller’s diarrhea
Inflammatory bowel disease
Cancers
Necrotizing enterocolitis
Breast milk jaundice
Hospital acquired pneumonia
Neonatal seizures