During this study patients will be assessed to determine the level of pain caused by their mucositis. This will occur before the first dose, one hour after the first dose, and then daily until they are no longer on the study. Patients will use the mouthwash by swishing and spitting (20mg/5ml) four times each day, and also every four hours as needed. Patients will use the mouthwash on this study until their mucositis gets better or until the mucositis gets worse (or if the pain does not get better after three days of treatment).