Introduction

Frey’s syndrome  was first described by Łucja Frey, a Polish and Jewish neurologist in 1923. It’s characterised by unilateral sweating and flushing of the facial skin during meals, typically around the parotid gland. It results from damage to the auriculotemporal nerve, which regulates saliva production. This damage, often caused by parotidectomy or facial trauma, leads to misdirected fibres of the parasympathetic system, which reinnervate sweat glands and blood vessels. As a result, gustatory stimuli trigger sweating, flushing, and warmth in areas near the ear and jaw. Symptoms vary in severity and are worsened by foods that stimulate salivation.¹ 

Importance of managing sweating in Frey’s syndrome

A person with Frey’s syndrome often experiences social embarrassment due to profuse sweating and flushing during eating. Over 80% of people are seen to have gustatory sweating — the sweat due to meals 40% report skin rush, and 20% report a rise in skin temperature.² There are several studies that indicate the impact of the Frey’s syndrome, grading the severity of symptoms along with social embarrassment.^2,3 Unfortunately, there is no standard questionnaire for evaluating this social embarrassment.²

Pathophysiology 

After nerve damage, postganglionic parasympathetic fibres aberrantly reinnervate the sweat gland which is previously controlled by sympathetic fibres. This miswiring in the facial region gives sympathetically denervated. 

During mastication, acetylcholine, which meant to be released for salivation, is now triggering sweating and flushing, a sympathetic response to heat or stress now shifted to parasympathetic system, leading to Frey’s syndrome.⁴ 

Role of antiperspirant in managing sweating

Antiperspirants are products that reduce sweating and perspiration on the skin. They play a major role in reducing sweating caused due to Frey's syndrome and hyperhidrosis. One of the most commonly used antiperspirants is aluminium chloride hexahydrate. 

Acetylcholine is a neurotransmitter that stimulates the eccrine glands to produce sweat. Aluminium chloride hexahydrate works by releasing the aluminium ions, which block the acetylcholine and in turn reduce sweating. The aluminium ions not only prevent the release of acetylcholine but also reduce the activity of the apocrine gland, which is responsible for excessive sweating in the case of Frey's syndrome.⁵ 

Other topical treatments for Frey's syndrome

Anticholinergic drugs 

Anticholinergic drugs such as scopolamine are used in managing sweat produced during Frey's syndrome. Scopolamine can easily penetrate through skin and blocks the nerve cells where acetylcholine acts as a neurotransmitter. Scopolamine's anticholinergic effect blocks the acetylcholine activity and helps in reducing sweat production. It also reduces the activity of parasympathetic nervous system which is involved in excessive sweating. 

It can be used in either solution form or cream form. 0.25℅ to 3℅ of scopolamine is used in solution form whereas 0.5℅ to 2℅ of scopolamine is used in cream form.⁶ 

Botulinum toxin type A

Intracutaneous injection of botulinum toxin type A (BoNT A) is an effective way of treating Frey's syndrome. BoNT A binds with the presynaptic neurons by blocking the acetylcholine thus reducing the sweat production. Blocking of acetylcholine leads to a temporary reduction in the activity of sweat and salivary glands. It also reduces the salivary gland activity, which contributes to treating Frey's syndrome. 

The injection is given at a concentration of 2 - 5 U/ml. It has minimal side effects and a high success rate.⁷^,⁸ 

Future implications 

The management of Frey's syndrome is expected to evolve with ongoing research and advancements in treatment options, which include: 

• Further research on optimising dosage regimens and application techniques for existing treatments will enable healthcare providers to tailor treatment plans to individual patient needs, leading to improved outcomes 
• Developing new formulations, like sprays or wipes, and innovative delivery methods may enhance patient compliance and make treatments more accessible, leading to better management of Frey's syndrome 

Summary 

Frey's syndrome, a rare neurological disorder characterised by excessive sweating and flushing in the facial area, can significantly impact a patient's quality of life. Fortunately, various treatments, including aluminium chloride hexahydrate antiperspirant, anticholinergic medications, and BoNT-A injections, have shown efficacy in managing this condition. By adopting a multidisciplinary approach and creating personalised treatment plans, healthcare providers can optimise outcomes for patients with Frey's syndrome. As research continues to advance, the development of novel formulations, combination therapies, and innovative delivery methods holds promise for improved treatment efficacy and enhanced patient care. Ultimately, a comprehensive understanding of Frey's syndrome and its management will enable healthcare providers to deliver high-quality, patient-centered care, improving the lives of those affected by this condition.