This was supported by immunohistochemical studies which have demonstrated a significant loss of epithelial and subepithelial nerve fibres [19,21] together with an increased expression of nerve growth factor (NGF) [22], transient receptor potential cation channel subfamily V member 1 (TRPV1) ion channels, as well as cannabinoid receptor type 2 (CB2) in modulating P2X3 receptors in the primary afferent neuron of tongue mucosa of BMS patients and associated with some changes in trigeminal reflexes [20,23,24]. This evidence concerns the gene NGF and burning mouth syndrome.