Probiotics may reduce the incidence and severity of OM caused by cancer treatment [26]. Cordeiro et al. showed that probiotic drinks effectively prevented mucositis in mice and concluded that the prevention of mucositis depends on the bacterial strain [45]. They also showed that probiotic products could be used to reduce the side effects of chemotherapy using generally recognized as safe (GRAS) bacteria by strengthening the immune system [46]. Streptococcus sali-varius K12 can reduce radiotherapy-induced OM in mice and is a promising treatment for cancer patients undergo-ing radiation therapy [47]. They also showed that Bacillus clausii UBBC-07 efectively delayed the onset and reduced the recovery time of OM, especially in the prevention of acute OM [48].