Inclusion Criteria:  Patients willing to sign the informed consent form Patients older than 18 years Patients with diagnosis of HNC, who had received local radiotherapy at least three months before the beginning of the study, involving the salivary glands, both for curative and palliative purpose, with or without chemotherapic treatment, reporting xerostomia symptoms Patients with diagnosis of HNC, who had received local radiotherapy as an adjuvant to surgical resection at least three months before the beginning of the study, with or without chemotherapic treatment, reporting xerostomia symptoms-  Exclusion Criteria:  Patients with documented contraindication to any of the components of GUM HYDRAL (there included eccipients) Patients with any neurological and psychiatric condition having an influence on the ability to self-apply the treatment Patients unwilling to complete the request diary card Patients unable to attend the ambulatory visits scheduled by the protocol Patients participating to other clinical studies Patients who had received antitumoral treatment during the previous three months Patients with concomitant Sjogren's syndrome Other causes of xerostomia (pharmacological treatment)