In a randomized clinical trial with patients receiving chemotherapy for cancer, it was discovered that 333 mg/mL Olea europaea leaf extract significantly reduced the expression of two pro-inflammatory cytokines, interleukin-1 beta (IL-1b) and TNF alpha (TNF-a), after 2 weeks and prevented the development of severe oral mucositis [61]. This evidence concerns the gene TNF and oral mucositis.