There are no side effects associated with the use of probiotics. All EU-registered probiotics have to pass stringent safety trials before being approved for use in each species. Probiotics have never been found to be toxic. Even more than 100 times, the recommended level does not cause any problems. It is also not possible to give too great a quantity of probiotics as any excess will pass out in the faeces. Only pathogenic bacteria can become overpopulated within the intestines which will result in the development of diarrhoea. Giving probiotics on a daily basis will prevent this from happening.