A non-powered device intended to be used during a chemotherapy treatment session for the application of cold/freezing temperatures to the oral cavity to help prevent and/or reduce symptoms associated with oral mucositis caused by chemotherapy (e.g., swelling, pain, mouth sores, bleeding gums). It is designed to be chilled in a freezer prior to use, and is in the form of a synthetic polymer mouthguard placed in front of the teeth with an external chamber containing water designed to be periodically squeezed by the patient to circulate cold water through the device. This is a reusable device.