Botulinum toxin is a widely accepted, effective treatment for Frey's syndrome. While some patients need only one injection, others require repeated treatments. We aimed to describe the clinical features of patients with a more challenging treatment course.

Literature review and retrospective analysis of eight consecutive patients treated at a university hospital.

These patients' treatment responses were categorised (using our own system) and compared with those of 25 published cases.

Combined analysis identified no significant correlation between treatment response and age, gender or the extent of primary salivary gland surgery. There was no significant correlation between botulinum toxin dosage and time between treatments.

Frey's syndrome should be viewed as a dynamic process in which the stimulus for aberrant reinnervation of parasympathetic nerve fibres can be reduced, in some patients, with higher botulinum toxin dose injections to the treated areas. However, responses are unpredictable, and relapses may occur at different time points and in different areas.

We report the previously undocumented complication of gustatory itching following superficial parotidectomy.

Case report and review of the English literature concerning Frey's syndrome, complications of superficial parotidectomy and the pathophysiology of itching.

A 49-year-old woman developed gustatory itching following a superficial parotidectomy. Her symptoms were satisfactorily managed with topical and oral antihistamine preparations. We propose a neurophysiological pathway involving acetylcholine and histamine to explain this phenomenon.

To our knowledge, this is the first documented case of gustatory itching following superficial parotidectomy. The use of antihistamine preparations appears to effectively manage this symptom, without the need for invasive procedures.

To measure patient-reported quality of life before and after botulinum toxin A treatment of post-parotidectomy Frey's syndrome (gustatory sweating).

A questionnaire concerning functional, social and emotional aspects of Frey's syndrome (14 questions, with responses on a zero to three point scale) was administered to 17 patients (13 women and four men) before and one month after intradermal injection of botulinum toxin A. Parotidectomy had been performed one to 19 years previously, for benign (n = 10) or malignant (n = 7) tumours, with gustatory sweating occurring a median of 15 months after surgery (range: one month to 14 years). Pre- and post-treatment quality of life scores were compared using Wilcoxon's test (p < 0.05).

Patients' reported functional quality of life improved significantly (p = 0.0004). Their social and emotional scores were not significantly modified (p = 0.155 and 0.142, respectively). Seven patients (41 per cent) found the injections painful, but all patients said that the effects were beneficial, that they would undergo new injections if necessary and that they would recommend this treatment to other patients. The benefit lasted over 1.5 years for 60 per cent of patients. No correlation was found between duration of the effect and the extent of parotidectomy (p = 0.067).

Botulinum toxin A significantly improved patients' functional quality of life, without significant improvement in their social or emotional quality of life, according to our questionnaire results. The duration of the effect was longer than the reported physiological effect of botulinum toxin A on acetylcholine receptors.