Oral mucositis is one of the most common complications of cancer therapy. It is a nonhematologic complication of cytotoxic chemotherapy and radiotherapy and reduces the quality of life. It is estimated that 40% the cases on standard chemotherapy may develop oral mucositis. Patients receiving radiation, especially in the cases of head and neck cancer, have 30%–60% chances of developing mucositis. Chemotherapy and radiotherapy interfere with the normal turnover of epithelial cells, leading to mucosal injuries. These injuries can also occur due to indirect invasion of Gram negative bacteria and fungi as most of the chemo-therapeutic agents will cause neutropenia and will give a favorable environment for the development of mucositis. The patient-related factors are also responsible for developing mucositis in chemo-induced and radiation-induced mucositis. Poor oral hygiene may also be responsible for bacterial super infection followed by chemotherapy. Mucositis is of two kinds: direct and indirect mucositis. Direct mucositis - The epithelial cells of the oral mucosa undergo rapid turnover in usually 7–14 days due to which these cells are more susceptible to the effect of the cytotoxic therapy which results in oral mucositis. Indirect mucositis – it can develop due to the infection caused by Gram-negative bacteria and fungal infection. There will be a greater risk for oral infection due to neutropenia. The onset of mucositis secondary to mylo-suppression varies depending upon the timing of the neutrophil count associated with chemotherapy agents but they typically develop around 10–21 days after chemotherapy administration.