Radiotherapy for head and neck cancer may cause the lining of the mouth and throat to become inflamed and sore during treatment. This lining is called the oral mucosa and when this inflammation develops, it is referred to as mucositis. Mucositis is usually treated with pain relief, mouth washes and a change of diet to soft or liquid foods. One approach which may help the symptoms of mucositis is to use a humidifier. which allows warm moist air to be delivered to the lining of the mouth and throat which has a moisturising effect on the mucosa. The aims of this study is to address two specific questions: Whether moisturising the mucosa will help make some of the symptoms of mucositis less severe, such as pain with swallowing and difficulty clearing sticky secretions from the throat To determine whether moisturising the mucosa may lead to earlier healing of the mucositis and faster resolution of symptoms