Sir, My Son Aged 2years Six Months Is Having Diareah,

sir,
My son aged 2years six months is having diareah, yesterday he had blood in his stool,
our doctor has prescribed entrogermina liquid 2times a day, zn20 for 2weeks (5ml two times a day) & rcifax syrup (5ml four times a day for three days. Please advice & also guide the reason for blood in the stool