An Overview of Frey Syndrome (Gustatory Sweating)

Frey syndrome is a rare neurological condition that causes facial sweating and flushing while eating. This can occur on the temples, cheeks, and behind the ears. Frey syndrome is also known as gustatory hyperhidrosis, gustatory sweating, and auriculotemporal syndrome.

The facial sweating and flushing in Frey syndrome is due to damage to the auriculotemporal nerve, which runs down the side of the face. Such damage can be caused by surgery to the parotid glands (which sit in front of the ears), a facial injury, or an illness like shingles.

In most people, Frey syndrome goes away on its own within a period of five years. Treatment is available if desired, with Botox being the most effective option.

This article discusses signs and symptoms of Frey syndrome, what causes it, how it is diagnosed, and what can be done if it is negatively affecting your quality of life.

Signs and Symptoms of Frey Syndrome

Common signs and symptoms of Frey syndrome, which would be present when eating or sometimes just thinking or talking about food, include:

• Facial sweating
• Facial flushing and redness
• General discomfort felt at cheek level

Frey syndrome can occur on only one side of the face or on both sides. In either case, the sweating and flushing will occur along the auriculotemporal nerve, which provides sensation to the side of the head.

As such, you may notice symptoms and signs in areas including:

• Cheeks
• Temples
• Behind your ears

Less Common Signs and Symptoms

Less commonly, people may feel warmth or pain with chewing.

In some people, an asymmetric pattern of sweating can also affect the trunk, arms, and legs. The more body surface area affected, the more severe the symptoms.

What Causes Frey Syndrome?

Frey syndrome is the most common type of gustatory sweating. It can happen at any age and is an abnormal response of the parotid gland and auriculotemporal nerve.

The parotid gland is the largest of the salivary glands. You have one on each side of your face in front of and just a bit down from your ears. These glands secrete saliva, which helps digest and moisten food.

The auriculotemporal nerve is involved in the reflex that releases that saliva in response to food.

In people with Frey syndrome, the nerve is injured and its parasympathetic fibers regrow abnormally. Instead of just stimulating salivation, it triggers sweating and flushing as well.

Anything that damages the auriculotemporal nerve can result in Frey syndrome.

Parotid Gland Surgery

Parotid gland surgery is the biggest cause of damage to the auriculotemporal nerve that results in Frey syndrome.

Roughly 10% of parotid surgery patients report symptoms of gustatory sweating. However, it can take up to 12 months to occur and may actually affect 30% to 50% of patients.

Injury, Infection, and Other Surgeries

Other possible causes of auriculotemporal nerve damage include:

• Blunt trauma to the cheek
• Chronic infection of the parotid gland
• Fracture of the jawbone or temporomandibular joint, which connects the jawbone to the skull
• Surgery on the temporomandibular joint
• Neck surgery
  
• Removal of the submandibular glands
• Removal of the thyroid gland
  
• Thoracic sympathectomy (a surgery done to control sweating)

Birth Trauma

In infants, damage to the auriculotemporal nerve can be caused by birth trauma or injury following forceps delivery.

Nevertheless, this is rare in infants and children. When it does occur, signs may be mistaken for those of a food allergy. However, an allergic reaction to food occurs after the ingestion of food not during it.

Other Nerve Conditions

Frey syndrome can also occur alongside other neurological conditions. These include:

• Chorda tympani injury
• Cluster headache
• Diabetic neuropathy
• Encephalitis
• Facial herpes zoster (shingles)
• Syringomyelia
• Tumor in the cervical sympathetic trunk
  

Diagnosis

Diagnostic testing for Frey syndrome can be done using a few different techniques, ranging from the simple Minor test and tissue test to more sophisticated biosensoring and thermography.

Only 10% to 15% of people who experience gustatory sweating actually seek medical attention for it. But if the condition is substantially impacting your quality of life and ability to socialize, it is worth a trip to your healthcare provider.

Minor Test

A procedure called the Minor test is the most common way to diagnose Frey syndrome.

This involves applying iodinated starch (indicator) powder to the face then eating something sweet. Areas where sweat droplets form turn blue-black.

Tissue Test

A less complex test involves applying one-ply tissue paper to the face. You are then given a sweet food to eat.

If sweating occurs, wet spots will be evident on the tissue paper.

Biosensoring

Biosensoring uses enzymatic electrodes that detect L-lactate levels on the skin. This is a more expensive diagnostic option.

Thermography

Thermography, or thermal imaging, displays skin temperature on a monitor. Special cameras are used to pick up these readings.

For this diagnostic test, you are given something sweet to eat to stimulate gustatory sweating. If Frey syndrome is present, infrared technology will produce a "hot spot" on a computer screen that corresponds to the dilation of subcutaneous blood vessels appears. Then, a "cold spot" representing gustatory sweating will appear.

Frey Syndrome Treatments

People with mild symptoms should be assured that the condition will pass on its own without treatment. In those seriously impacted by gustatory sweating, Botox, antiperspirants, topical medications, and surgery may be considered.

Botox

Evidence-based research points to Botox therapy as the most promising and successful way to treat the gustatory sweating and flushing of Frey syndrome.

More specifically, Botox therapy has proven to be 98% effective in treating symptoms of gustatory sweating. Treatment has also proven to be effective in people who experience gustatory sweating secondary to diabetic neuropathy, a type of nerve damage due to diabetes.

Botox therapy for Frey syndrome starts with the clinician identifying the affected area using the Minor test. This area is then visually divided into several smaller squares, which are between 1 and 1.5 cm. Botox is then injected into each of these squares.

Antiperspirants

Antiperspirants can be applied to the area affected by gustatory sweating. Some patients have reported limited improvement for a period of several weeks thanks to antiperspirants.

However, antiperspirants can irritate the skin and cause inflammation. They can also enter the eye, which can cause irritation and complications that cause pain and blurry vision.

For best results, apply a gel antiperspirant to dry skin at night. You can allow it to air dry or use a hairdryer on a cool setting. Wash the antiperspirant off in the morning. Avoid shaving the treated area with anything for 12 hours after application.

Over time, antiperspirant treatments can be done on alternating days, then slowly spaced out further. As the condition runs its course, you won’t need to apply antiperspirants as often.

Topical Anticholinergics

Topical anticholinergics used to treat Frey syndrome include:

• Scopolamine
• Glycopyrrolate
• Diphemnanilmethylsulfate

These medication are applied as roll-on solutions or creams and improve symptoms for about three days.

Side effects of topical anticholinergics include:

• Dry mouth
• Blurred vision
• Itchy eyes
• Urinary retention
• Increased heart rate
• Allergies

Anticholinergics should not be used in people with:

• Central nervous system diseases
• Diabetes
• Glaucoma
• Heart disease
• Kidney disease
• Liver disease
• Obstructive uropathy
• Thyroid disease

Surgical Options

Surgeries used to treat Frey syndrome include:

• Cervical sympathectomy
• Tympanic neurectomy
• Sternocleidomastoidtransfer transfer
• Dermis-fat grafts

However, these procedures have had limited success in relieving Frey syndrome. In addition, most people who develop gustatory sweating secondary to surgery are reluctant to receive more surgery to treat this condition.