Frey's syndrome

Gustatory sweating and flushing caused by aberrant auriculotemporal nerve regeneration

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Frey's syndrome
Synonyms	Frey syndrome, auriculotemporal syndrome, gustatory sweating, Frey-Baillarger syndrome, Baillarger syndrome, auriculotemporal nerve syndrome
Pronounce	N/A
Specialty	Otolaryngology, Neurology, Dermatology, Oral and maxillofacial surgery
Symptoms	Sweating, flushing, warmth, tingling, or discomfort over the cheek or temple during eating
Complications	Social embarrassment, skin irritation, recurrent sweating, reduced quality of life
Onset	Usually months to years after parotid surgery, facial trauma, or nerve injury
Duration	Chronic or recurrent
Types	N/A
Causes	Aberrant regeneration of parasympathetic fibers of the auriculotemporal nerve
Risks	Parotidectomy, parotid trauma, mandibular condyle fracture, facial surgery, birth trauma, infection near the parotid region
Diagnosis	Clinical history, food-triggered sweating, Minor's iodine-starch test, thermography
Differential diagnosis	Primary focal hyperhidrosis, facial flushing, food allergy, gustatory rhinitis, rosacea, diabetic gustatory sweating
Prevention	Surgical barrier techniques during parotidectomy in selected patients
Treatment	Reassurance, topical antiperspirants, topical anticholinergics, botulinum toxin injections, rarely surgery
Medication	Botulinum toxin A, topical anticholinergics, aluminum chloride antiperspirant
Prognosis	Usually benign; symptoms often improve with treatment
Frequency	Common after parotid surgery, but symptomatic severe disease is less common
Deaths	N/A

Frey's syndrome is a disorder of abnormal sweating and flushing over the cheek, temple, ear, or upper neck that occurs during eating, smelling food, thinking about food, or other stimuli that normally cause salivation. It is also called auriculotemporal syndrome or gustatory sweating. The condition most often follows injury to the auriculotemporal nerve after parotidectomy, trauma, infection, or other surgery near the parotid gland."Frey's Syndrome: A Review of Aetiology and Treatment".Cureus.2021;PMC:8638782.

Frey's syndrome is usually benign but may be distressing because eating can trigger visible facial sweating, warmth, redness, or dripping sweat. Diagnosis is usually clinical and may be confirmed by Minor's iodine-starch test. The most widely used treatment for troublesome symptoms is intradermal injection of botulinum toxin type A, which can reduce sweating for months and may be repeated when symptoms recur."Use of botulinum toxin in Frey's syndrome".Clinical Case Reports.2019;PMC:6406149."Treatment of Frey Syndrome with Botulinum Toxin-A".Cureus.2023;PMC:11001827.

Overview

Frey's syndrome occurs when nerve fibers that normally stimulate salivation regrow abnormally and connect to sweat glands or blood vessels in the overlying skin. As a result, the same stimulus that should make the parotid gland produce saliva instead causes sweating and flushing in the skin supplied by the auriculotemporal nerve.

The classic setting is after parotid gland surgery, especially parotidectomy for benign or malignant salivary gland tumors. It can also occur after facial trauma, mandibular condyle fracture, infection, burns, or rarely in children after birth trauma. In infants and children, Frey's syndrome may be mistaken for food allergy because facial redness occurs during feeding."Auriculotemporal Frey syndrome not associated with surgery or diabetes: systematic review".European Journal of Pediatrics.2022;PMC:9056449.

Terminology

• Frey's syndrome - Common eponym for gustatory sweating due to auriculotemporal nerve dysfunction.
• Auriculotemporal syndrome - Descriptive term based on the nerve involved.
• Gustatory sweating - Sweating triggered by taste, chewing, or food-related stimuli.
• Frey-Baillarger syndrome - Historical eponym sometimes used for the condition.
• Baillarger syndrome - Historical name reflecting early description by Baillarger.
• Auriculotemporal nerve syndrome - Another descriptive term for the syndrome.
• Gustatory hyperhidrosis - Excessive sweating triggered by eating or gustatory stimuli.

Signs and symptoms

The symptoms are usually localized and triggered by food-related stimuli.

• Gustatory sweating - Sweating over the cheek, temple, ear region, or upper neck during eating.
• Facial flushing - Redness over the affected area during chewing, tasting, or thinking about food.
• Warmth - Feeling of heat over the involved cheek or temple.
• Paresthesia - Tingling or altered sensation may occur in the affected skin.
• Burning pain - Some patients describe burning discomfort.
• Pruritus - Itching may occur in some cases.
• Facial erythema - Visible redness can accompany sweating.
• Unilateral symptoms - One-sided symptoms are most common after one-sided parotid surgery.
• Bilateral symptoms - Can occur after bilateral surgery or systemic neurologic causes.
• Social embarrassment - Visible sweating during meals may reduce quality of life.
• Skin irritation - Repeated sweating or wiping may irritate the skin.

Symptoms may be triggered by sour foods, spicy foods, chewing, salivary stimulation, smell of food, or even thinking or talking about food. A lemon wedge, sour candy, or other salivary stimulant is sometimes used during diagnostic testing.

Causes

Frey's syndrome is caused by injury and abnormal regeneration of autonomic nerve fibers near the parotid gland.

• Parotidectomy - The most common cause in adults.
• Superficial parotidectomy - Removal of the superficial lobe of the parotid may injure regional nerves.
• Total parotidectomy - Removal of the entire parotid can increase risk.
• Parotid tumor surgery - Surgery for pleomorphic adenoma, Warthin tumor, or malignant salivary tumors may be followed by Frey's syndrome.
• Mandibular condyle fracture - Trauma near the auriculotemporal nerve can cause the syndrome.
• Facial trauma - Lacerations, burns, or blunt trauma can injure autonomic fibers.
• Parotitis - Infection or inflammation near the parotid may rarely lead to symptoms.
• Temporomandibular joint surgery - Surgery near the auriculotemporal nerve can rarely cause symptoms.
• Neck dissection - Regional surgery may contribute in selected cases.
• Diabetic autonomic neuropathy - Can cause gustatory sweating, usually with a different distribution.
• Birth trauma - Pediatric cases may follow forceps-assisted delivery or local nerve injury.

Pathophysiology

The auriculotemporal nerve is a branch of the mandibular division of the trigeminal nerve. It carries sensory fibers from the temporal region and parasympathetic secretomotor fibers to the parotid gland.

• Auriculotemporal nerve - Nerve most closely associated with Frey's syndrome.
• Trigeminal nerve - Cranial nerve whose mandibular division gives rise to the auriculotemporal nerve.
• Mandibular nerve - V3 division of the trigeminal nerve.
• Otic ganglion - Parasympathetic ganglion involved in parotid secretomotor pathways.
• Parotid gland - Salivary gland normally stimulated during eating.
• Sweat gland - Abnormally stimulated after misdirected nerve regeneration.
• Parasympathetic nervous system - Normally stimulates salivation.
• Sympathetic nervous system - Normally controls sweating and vasomotor tone.
• Aberrant nerve regeneration - Incorrect nerve regrowth after injury.
• Synkinesis - Involuntary movement or response occurring with a voluntary or reflex action.

After nerve injury, postganglionic parasympathetic fibers intended for the parotid gland can regenerate toward sweat glands and cutaneous blood vessels. When the patient eats, these fibers activate sweating and flushing instead of only stimulating saliva production.

Risk factors

The risk of Frey's syndrome depends on the underlying injury, surgical approach, extent of parotid surgery, and preventive measures.

• Parotidectomy - Major risk factor.
• Large parotid tumor - May require more extensive surgery.
• Revision surgery - Repeat surgery may increase nerve injury risk.
• Facial nerve dissection - Surgical manipulation near the parotid and facial nerve can increase risk.
• Thin skin flap - May allow closer contact between regenerating nerves and sweat glands.
• No interposition barrier - Lack of tissue barrier between parotid bed and skin may increase risk.
• Trauma - Injury near the ear, cheek, mandible, or temporal region can cause the syndrome.
• Diabetes mellitus - Can be associated with gustatory sweating through autonomic neuropathy.
• Childbirth trauma - Forceps-related facial nerve region injury may cause pediatric auriculotemporal syndrome.

Diagnosis

Diagnosis is usually based on the typical history of food-triggered sweating or flushing in the auriculotemporal distribution, especially after parotid surgery or facial trauma.

Clinical evaluation

• Medical history - Reviews parotid surgery, trauma, infection, facial procedures, diabetes, and symptom triggers.
• Physical examination - Evaluates the location of flushing, sweating, scars, and sensory changes.
• Food challenge - Sour or salivary-stimulating food may provoke symptoms.
• Symptom diary - Patient records food triggers, sweating area, severity, and duration.
• Quality of life assessment - Helps decide whether treatment is needed.
• Medication review - Identifies drugs or conditions that can cause sweating or flushing.

Minor's iodine-starch test

Minor's iodine-starch test is the classic confirmatory test.

• Iodine - Applied to the affected skin and allowed to dry.
• Starch - Powdered starch is applied over the iodine.
• Salivary stimulus - Patient eats or tastes sour food to provoke sweating.
• Color change - Sweat causes the iodine-starch mixture to turn dark blue, purple, or black.
• Mapping - The colored area identifies the region for botulinum toxin injection.
• Treatment planning - The test can guide injection spacing and dose distribution.

Other diagnostic methods

• Thermography - Infrared imaging may show temperature changes associated with flushing and sweating.
• Gravimetry - Measures sweat quantity in research settings.
• Questionnaire - Patient-reported symptom scales may help grade severity.
• Photographic documentation - Used to compare severity before and after treatment.
• Neurologic examination - Useful when symptoms are atypical or associated with other nerve findings.
• Imaging - Usually not required unless recurrent tumor, mass, or another local lesion is suspected.

Differential diagnosis

The differential diagnosis includes other causes of facial sweating, flushing, food-related reactions, or autonomic symptoms.

• Primary focal hyperhidrosis - Excessive sweating unrelated to salivary stimulation.
• Craniofacial hyperhidrosis - Excess sweating of the head and face.
• Rosacea - Chronic facial flushing and inflammatory skin disease.
• Food allergy - Can cause flushing or rash after eating, especially in children.
• Gustatory rhinitis - Runny nose triggered by eating.
• Diabetic gustatory sweating - Autonomic neuropathy causing sweating with meals.
• Carcinoid syndrome - Flushing, diarrhea, and systemic symptoms from neuroendocrine tumor.
• Mast cell activation syndrome - Episodic flushing and allergic-type symptoms.
• Menopause - Hot flashes may cause facial flushing and sweating.
• Medication-induced flushing - Niacin, vasodilators, alcohol, and other drugs can cause flushing.
• Harlequin syndrome - Asymmetric facial flushing and sweating due to autonomic dysfunction.
• Horner syndrome - Ptosis, miosis, and anhidrosis from sympathetic pathway disruption.
• Complex regional pain syndrome - Autonomic changes with pain after injury.
• Recurrent parotid tumor - Should be considered if new mass, pain, or progressive local symptoms occur.

Management

Treatment depends on severity. Mild symptoms may need only reassurance. Moderate or severe symptoms may require topical therapy, botulinum toxin injection, or rarely surgery.

Conservative management

• Reassurance - Appropriate for mild, non-bothersome symptoms.
• Trigger avoidance - Avoiding very sour or spicy foods may reduce attacks in some patients.
• Skin care - Gentle cleansing and barrier protection may reduce irritation.
• Patient education - Explains the benign mechanism and available treatments.
• Observation - Some cases are stable or improve over time.

Topical treatment

Topical treatments may help mild cases but are often temporary or limited by irritation.

• Aluminum chloride - Topical antiperspirant that can reduce sweating.
• Anticholinergic drug - Topical anticholinergic preparations may reduce sweating.
• Glycopyrrolate - Anticholinergic agent used topically or systemically in selected cases.
• Scopolamine - Anticholinergic sometimes reported for topical use.
• Skin irritation - Common limitation of topical agents.
• Dry mouth - Possible anticholinergic side effect.
• Glaucoma - Anticholinergic drugs require caution in susceptible patients.
• Urinary retention - Anticholinergic therapy may worsen urinary retention.

Botulinum toxin

Botulinum toxin injection is widely regarded as the most effective practical treatment for symptomatic Frey's syndrome.

• Botulinum toxin type A - Most commonly used injectable treatment.
• Intradermal injection - Injection is placed into the skin of the affected area.
• Minor's iodine-starch test - Used to map the sweating region before injection.
• Acetylcholine - Botulinum toxin blocks acetylcholine release at cholinergic nerve endings.
• Sweat reduction - Decreased stimulation of sweat glands reduces gustatory sweating.
• Repeat treatment - Symptoms may recur after months and can be treated again.
• Local weakness - Rare complication if toxin spreads to nearby muscles.
• Dryness - Local dryness may occur after treatment.
• Patient satisfaction - Often high when symptoms are socially or functionally bothersome.

Published reports and reviews suggest that botulinum toxin A can improve sweating within days and may provide benefit for several months, though duration varies among patients."Use of botulinum toxin in Frey's syndrome".Clinical Case Reports.2019;PMC:6406149."Treatment of Frey Syndrome with Botulinum Toxin-A".Cureus.2023;PMC:11001827.

Surgical treatment

Surgery is rarely first-line treatment for established Frey's syndrome because less invasive treatments are usually preferred.

• Tympanic neurectomy - Historical procedure to interrupt secretomotor pathways.
• Auriculotemporal nerve surgery - Rarely performed because of recurrence and potential morbidity.
• Interposition flap - Tissue barrier placed between parotid bed and skin.
• Sternocleidomastoid flap - Muscle flap sometimes used during parotid reconstruction.
• Superficial musculoaponeurotic system flap - May reduce Frey's syndrome after parotidectomy.
• Temporoparietal fascia flap - Barrier flap used in selected reconstructive settings.
• Acellular dermal matrix - Barrier material used by some surgeons to reduce postoperative Frey's syndrome.
• Surgical revision - Considered only for severe, refractory, or reconstructive cases.

A 2025 review of surgical treatment reported that surgery may be considered for selected patients with severe symptoms, failed medical treatment, tumor recurrence, or unsatisfactory surgical sequelae, but medical treatment remains preferred for most patients."Frey's Syndrome Surgical Treatment After Parotidectomy".Journal of Clinical Medicine.2025;14(2)

415.doi:10.3390/jcm14020415.

Prevention

Prevention is mainly considered during parotid surgery.

• Careful surgical technique - Reduces unnecessary nerve and tissue trauma.
• Thick skin flap - May reduce contact between regenerating nerve fibers and sweat glands.
• Barrier interposition - Separates the parotid bed from overlying skin.
• Sternocleidomastoid muscle flap - May be used to fill the surgical defect.
• Superficial musculoaponeurotic system flap - May reduce postoperative Frey's syndrome.
• Temporoparietal fascia flap - Used in selected reconstructive procedures.
• Acellular dermal matrix - Barrier graft used in some parotidectomy patients.
• Free fat graft - May be used for contour restoration and barrier effect.
• Patient counseling - Patients undergoing parotidectomy should be informed of the risk.

A Cochrane review on graft interposition after parotidectomy found that interposition barriers may reduce Frey's syndrome, but the quality of evidence and certainty of benefit vary by technique and study design."Graft interposition for preventing Frey's syndrome in patients undergoing parotidectomy".Cochrane Database of Systematic Reviews.2019;(10)doi:10.1002/14651858.CD012323.pub2.PMID:31578708.PMC:6953270.

Complications

Frey's syndrome is not usually dangerous, but it can affect comfort and quality of life.

• Social embarrassment - Visible sweating while eating can be distressing.
• Avoidant behavior - Some patients avoid eating in public.
• Skin irritation - Repeated sweating and wiping may irritate the skin.
• Anxiety - Anticipation of symptoms can cause distress.
• Reduced quality of life - Severe symptoms may interfere with meals and social activity.
• Pain - Burning or neuralgic discomfort may occur in some patients.
• Recurrent symptoms - Symptoms may return after temporary treatments.
• Treatment side effects - Botulinum toxin or anticholinergics can cause local or systemic effects.

Prognosis

The prognosis is generally good. Frey's syndrome is usually benign and treatable.

• Benign disorder - It does not usually indicate a dangerous disease.
• Chronic course - Symptoms may persist for years if untreated.
• Treatment response - Botulinum toxin often provides meaningful improvement.
• Recurrence - Symptoms may recur as botulinum toxin wears off.
• Mild disease - Many patients do not need treatment.
• Severe disease - Can cause significant social or functional impairment.
• Postoperative counseling - Helps patients recognize symptoms and seek treatment.

Epidemiology

The true frequency is difficult to determine because many patients have mild or subclinical symptoms. Objective testing after parotidectomy detects gustatory sweating in a high proportion of patients, but fewer patients report symptoms as bothersome. Estimates vary by surgical method, follow-up duration, testing method, and definition of disease.

• Parotidectomy - Most common adult setting.
• Objective Frey's syndrome - Positive Minor test without major symptoms.
• Subjective Frey's syndrome - Patient-noticed sweating or flushing.
• Severe Frey's syndrome - Symptoms that affect quality of life or require treatment.
• Males and females - Both sexes can be affected.
• Pediatric Frey's syndrome - Rare and often associated with birth trauma or forceps delivery.

History

The disorder was first described in the medical literature before the modern eponym became common. It is named for Polish neurologist Łucja Frey, who gave a detailed description of auriculotemporal nerve syndrome in 1923.

• Baillarger - Reported an early description in 1853.
• Łucja Frey - Polish neurologist who described auriculotemporal syndrome in detail.
• Auriculotemporal syndrome - Term used by Frey to describe the condition.
• Parotidectomy - Later recognized as the most common cause.
• Minor's iodine-starch test - Became the standard method for mapping sweating.
• Botulinum toxin - Became the leading modern treatment for symptomatic disease.

Patient education

Patients should understand that Frey's syndrome is caused by nerve miswiring after injury or surgery and is usually not dangerous.

• Eating trigger - Sweating during meals is typical.
• Sour food - Sour foods may trigger stronger symptoms.
• Not food allergy - In children, one-sided facial flushing with eating can be mistaken for allergy.
• Treatment options - Mild symptoms may need no treatment, while bothersome symptoms can often be treated.
• Botulinum toxin - May reduce sweating for months and can be repeated.
• Skin care - Gentle skin care can reduce irritation.
• Postoperative symptom - Symptoms after parotid surgery should be discussed with the surgeon or clinician.
• Recurrent mass - New swelling or pain after parotid surgery should be evaluated separately.
• Quality of life - Treatment is appropriate when symptoms cause embarrassment or distress.

When to seek medical care

Medical evaluation is appropriate when symptoms are bothersome, new, atypical, or associated with other findings.

• Facial sweating - Sweating over one cheek or temple during eating should be evaluated if persistent or distressing.
• Facial flushing - Recurrent one-sided flushing with meals may suggest Frey's syndrome.
• Post-parotidectomy symptom - Sweating or flushing after parotid surgery should be reported.
• Facial pain - Persistent or severe pain needs evaluation.
• New parotid swelling - May require assessment for recurrent tumor, infection, or salivary disease.
• Fever - Fever with parotid pain or swelling may suggest infection.
• Food allergy concern - Children with meal-triggered facial redness should be evaluated to distinguish allergy from Frey's syndrome.
• Treatment failure - Persistent symptoms despite topical therapy may benefit from botulinum toxin assessment.
• Eye symptoms - Anticholinergic treatment should be reviewed if glaucoma risk exists.
• Urinary symptoms - Anticholinergics may worsen urinary retention.

See also

• Auriculotemporal nerve
• Parotid gland
• Parotidectomy
• Gustatory sweating
• Hyperhidrosis
• Botulinum toxin
• Facial flushing
• Trigeminal nerve
• Otic ganglion
• Salivary gland
• Salivary gland pathology
• Oral and maxillofacial surgery
• Otolaryngology
• Neurology
• Dermatology
• Diabetic autonomic neuropathy
• Minor's iodine-starch test

Further reading

• "Frey's Syndrome: A Review of Aetiology and Treatment".Cureus.2021;PMC:8638782.
• "Use of botulinum toxin in Frey's syndrome".Clinical Case Reports.2019;PMC:6406149.
• "Treatment of Frey Syndrome with Botulinum Toxin-A".Cureus.2023;PMC:11001827.
• "Graft interposition for preventing Frey's syndrome in patients undergoing parotidectomy".Cochrane Database of Systematic Reviews.2019;(10)doi:10.1002/14651858.CD012323.pub2.PMID:31578708.PMC:6953270.
• "Interventions for the treatment of Frey's syndrome".Cochrane Database of Systematic Reviews.2015;(3)doi:10.1002/14651858.CD009959.pub2.PMID:25781421.
• "Frey's Syndrome Surgical Treatment After Parotidectomy".Journal of Clinical Medicine.2025;14(2)

415.doi:10.3390/jcm14020415.

• "Auriculotemporal Frey syndrome not associated with surgery or diabetes: systematic review".European Journal of Pediatrics.2022;PMC:9056449.

External links

• NORD - Frey Syndrome
• Frey's Syndrome: A Review of Aetiology and Treatment
• Use of botulinum toxin in Frey's syndrome
• Cochrane - Graft interposition for preventing Frey's syndrome
• Cochrane - Interventions for the treatment of Frey's syndrome
• University of Iowa Head and Neck Protocols - Botulinum toxin injection for Frey's syndrome

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External links

• Comprehensive information from the National Institute of health.
  

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