Mucositis is the painful inflammation and ulceration of the mucous membranes lining the digestive tract, usually as an adverse effect of  chemotherapy and radiotherapy treatment for cancer. Mucositis can occur anywhere along the gastrointestinal (GI) tract, but oral mucositis refers to the particular inflammation and ulceration that occurs in the mouth. Oral mucositis is a common and often debilitating complication of cancer treatment.Oral and gastrointestinal (GI) mucositis affects almost all patients undergoing high-dose chemotherapy and hematopoietic stem cell transplantation (HSCT), 80% of patients with malignancies of the head and neck receiving radiotherapy, and a wide range of patients receiving chemotherapy. Alimentary tract mucositis increases mortality and morbidity and contributes to rising health care costs.For most cancer treatment, about 5–15% of patients get mucositis. However, with 5-fluorouracil (5-FU), up to 40% get mucositis, and 10–15% get grade 3–4 oral mucositis. Irinotecan is associated with severe GI mucositis in over 20% of patients. Seventy-five to eighty percent of bone marrow transplantation recipients experience mucositis, of which oral mucositis is the most common and most debilitating, especially when melphalan is used. In grade 3 oral mucositis, the patient is unable to eat solid food, and in grade 4, the patient is unable to consume liquids as well.Radiotherapy to the head and neck or to the pelvis or abdomen is associated with Grade 3 and Grade 4 oral or GI mucositis, respectively, often exceeding 50% of patients. Among patients undergoing head and neck radiotherapy, pain and decreased oral function may persist long after the conclusion of therapy.
Fractionated radiation dosage increases the risk of mucositis to > 70% of patients in most trials. Oral mucositis is particularly profound and prolonged among HSCT recipients who receive total-body irradiation. Signs and symptoms
Cancer patients undergoing chemotherapy usually become symptomatic four to five days after beginning treatment, reaching a peak at around day 10, and then slowly improving over the course of a few weeks. Mucositis associated with radiotherapy usually appears at the end of the second week of treatment and may last for six to eight weeks.As a result of cell death in reaction to chemo- or radio-therapy, the mucosal lining of the mouth becomes thin, may slough off and then become red, inflamed and ulcerated. The ulcers may become covered by a yellowish-white fibrin clot called a pseudomembrane. Peripheral erythema is usually present. Ulcers may range from 0.5 cm to greater than 4 cm. Oral mucositis can be severely painful. The degree of pain is usually related to the extent of the tissue damage. Pain is often described as a burning sensation accompanied by reddening. Due to pain, the patient may experience trouble speaking, eating, or even opening the mouth.Dysgeusia, or an alteration in taste perception, is common, especially for those who are receiving concomitant radiation therapy to the neck and mouth area. "Taste blindness", or an altered sense of taste, is a temporary condition that occurs because of effects on taste buds that are mostly located in the tongue. Sometimes, only partial recovery of taste occurs.