Diarrhoea is one of the most common side effects of chemotherapy in dogs, and can significantly impact the quality of life of dogs undergoing chemotherapy treatments. Based on our previous research, it is estimated that about 30-40% of dogs receiving vincristine or doxorubicin will develop diarrhoea. In humans, it has been found that gut bacteria can re-activate chemotherapy drugs, inducing gastrointestinal damage and consequently diarrhoea. Recent data suggest that aspartame, an artificial sweetener, appears to be promising in preventing gut bacteria to reactivate chemotherapy drugs.