Its probably food poisoning caused by the toxins of common bacteria such as E.coli, Staphylococci, Bacillus, Vibrios or Salmonella. If its dysentry ie blood n mucous present in loose stools, it may be shigellosis or amoebiasis. Most diarrhoeas will be self limiting conditions and subside in 2-3 days. The best treatment for such cases is Oral rehydration therapy as dehydration is the major threat. ORS salts are available over the counter. Keep drinking ORS at frequent intervals. However if it does not subside within 2-3 days I suggest you visit your physician for medication and have a stool microscopy and culture done to determine the exact cause.