Diarrhea Last How Long?

My baby has been having diarrhoea too. I brought her to the PD on day2 and my PD told me baby's diarrhoea will last for 7days. Unlike adults' diarrhoea which will only last for at most 2-3days. Your PD only prescribe your baby with probiotics? My PD gave me probiotics, hydration tablets(to replenish the loss of water) and hidrasec (to harden baby stools) . My PD told me that the medication he gave me will not stop my baby's diarrhoea immediately but will harden her stools.. If her diarrhoea still persist after a week then I will have to bring her to see him again to check her stools...