Background: Frey’s syndrome or Gustatory sweating was first described by Baillarger in 1853. Lucie Frey had described a patient as “auriculotemporal syndrome” in 1923. The explanation for this symptom has been an aberrant regeneration of postganglionic parasympathetic fibers feeding the parotid gland that are severed during parotidectomy. After parotidectomy, these cholinergic parasympathetic fibers regenerate and anastomosis with postganglionic sympathetic fibers that supply vessel and sweat gland of the skin. According to a recent study, the treatment of Frey’s syndrome has no treatment of choice. The authors investigated the effectiveness of botulinum toxin type A in the treatment of Frey’s syndrome for the first time in Thai patients.
Material and Method: The present study was a prospective non-randomized, exploratory study. Nine patients with a median involvement skin area of 4.2 cm2 (1-16.3) were injected intradermal with botulinum toxin type A 2 unit in every 1 cm2 of involved skin. The mean total dose was 10.6 units (range 2-32 unit).
Results: All of the patients showed improvement after 4-7 days. Five patients have no Gustatory sweating. In the same way, four patients present with a dramatic decrease in Gustatory sweating. When comparing the skin involvement area, indicated by Minor’s iodine starch test and calculated by program ImageJ 1.34s, between before and after injection of botulinum toxin type A using sign test, the result is statistically significant with p = 0.0039. The result lasted for 9.2 months (7-10 months).
Conclusion: Intradermal injection of botulinum toxin type A for patients with Frey’s syndrome is not only effective with no side effect but also minimally invasive. The present report supports that intradermal injection of botulinum toxin type A should be the treatment of choice for Frey’s syndrome.

Keywords: Frey’s syndrome, Gustatory sweating, Auriculotemporal syndrome, Botulinum toxin, BOTOX®