The effect of botulinum neurotoxin type A intradermal injection in will be evaluated in 4 patients with clinical diagnosis of burning mouth syndrome involving the anterior two-thirds of the tongue and the lower lip for at least 6 months, refractory to common pharmacological treatments. Pain severity will be measured by the visual analog scale (VAS) indicating average week pain before injection. Each patient will be injected with a total dose of 16 units (dilution: 2 ml saline) of incobotulinumA: 4 units into each side of the lower lip and 4 units into each antero-lateral side of the tongue. In order to determine if a placebo effect may be involved, we will inject 2 additional patients with saline solution using the same volumes and the same injection sites. Patients will be evaluated at 48 hours and then at 4, 8, 12, 16 and 20 weeks after the treatment. Patients treated with placebo will be treated after 4 weeks with incobotulinumA with the same dose reported above.

Inclusion Criteria:

• burning mouth syndrome

Exclusion Criteria:

• any other mouth disorder