Idiopathic burning mouth syndrome (BMS) is a chronic orofacial pain condition in which the pain is felt as intense, located on the tongue and the oral mucosa with no known cause. The pain may last for years and present treatments are of little effect. BMS is primarily a feminine disease, affecting women during or following menopause, suggesting an etiopathogenic role of the sexual hormones potentiating a local salivary factor. An anxiodepressive component is often associated with the disease. Recently, a molecule named opiorphin has been identified in human saliva. In animals, this molecule has shown potent analgesic properties comparable to those of morphine. The hypothesis of the investigators is that this molecule is in lower quantity in the saliva of persons suffering BMS and that this decrease causes oral burning sensations.