Chemotherapy-induced mucositis develops 5-10 days after the initiation of treatment and resolves slowly 2-3 weeks after cessation of treatment, usually when the absolute neutrophil count rises above 500/ml. It occurs in approximately 20%-40% of patients receiving conventional chemotherapy and 80% of patients receiving high-dose chemotherapy. It starts with erythema of the mucosa, which usually breaks down to form ulcers. Ulcers may be single or multiple, round or irregularly shaped, and are usually on sites that are frequently traumatized (eg, buccal mucosa).

While not all chemotherapeutic agents will cause mucositis, many of them have this capability. Some agents (eg, methotrexate and etoposide) are excreted in saliva, which increases their toxicity. The degree to which mucositis is induced is also dependent on the drug and the age of the patient, with younger patients often experiencing more severe signs and symptoms. Chemotherapy-induced mucositis tends to be less severe in patients who have received recombinant human granulocyte colony-stimulating factor (G-CSF). Patients complain of pain and burning that is exacerbated by eating and by oral hygiene procedures.

Oral mucositis combined with gastrointestinal mucositis may occur in about 8% of patients who receive standard-dose chemotherapy with subsequent development of myelosuppression. Suggestive symptoms include pain, nausea / vomiting, and diarrhea.