MOM's PAIN (Methylene Blue for Oral Mucositis' PAIN)

Inclusion Criteria: * Patients with a cancer diagnosis, receiving chemotherapy, radiation therapy or the combination * Patients with a current diagnosis of oral mucositis * Patients with pain and oral dysfunction associated with oral mucositis despite conventional therapy * Voluntary written consent * Patient must agree to use of contraception or abstinence from sex during the treatment period and for 30 days after patient's last dose Exclusion Criteria: * Patients with known allergy to MB * Patients taking medications with known significant drug interactions * Pregnant or lactating patients * Patients who are cognitively impaired and unable to consent for the study * Patients with risk of broncho-aspiration based on documented swallowing test by a speech pathologist (if available) * Patients with known history of G6PD deficiency * Patients undergoing any other experimental intervention for oral mucositis * Patients who have no pain or impairment in oral function, patients who are not symptomatic * Patients with head and neck cancer * Patients on serotonergic drugs