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A previously healthy three-year-old girl presented with a one-week history of an episodic erythematous patch extending from the corner of the mouth to the right cheek. The eruption occurred following eating, but on occasion would occur with teeth brushing and finger sucking. There was no associated pruritus, scale, vesicles, pustules, burning or scarring. The eruption was not associated with sun exposure.
Although the eruption seemed to be primarily associated with eating, it was not linked to any particular food. The flushing lasted from 30 min to 60 min, and did not show a response to either a midpotency topical corticosteroid or a topical antibiotic.
On review of systems, there were no associated symptoms of facial swelling, wheezing, urticaria, vomiting or abdominal pain. There was no history of involvement in other sun-exposed areas. The patient’s past medical history is only significant for a ventricular septal defect, previously spontaneously closed. Of note, there was no history of traumatic delivery.
The patient’s physical examination revealed a well-appearing young girl. Her vital signs were normal. She had a blanching erythematous patch extending from the right cheek to the right corner of her mouth (Figure 1). The rest of her examination was normal.
Reviewing the patient’s history and physical examination revealed the diagnosis.
Localized unilateral or bilateral facial flushing in the auriculotemporal nerve (ATN) territory (lateral cheek, medial ear and frontotemporal scalp) is known as Frey syndrome. It is often triggered by masticulatory or tactile stimuli and may also be associated with hyperhidrosis in the area.
The syndrome was originally described by Duphenix in 1757, and later by Bailarger in 1853, who reported this in patients following parotid abscess surgery. The condition later gained its eponym in 1923 after Frey made the pathophysiological association with the ATN.
The ATN arises as two roots from the posterior division of the mandibular nerve. It emerges on the face behind the temporomandibular joint within the surface of the parotid gland and supplies somatosensory and parasympathetic innervation to the face. The somatosensory component of the auriculotemporal nerve innervates the skin overlying the preauricular areas, tragus, auricle and temporal region. The parasympathetic component carries postganglionic fibres to the parotid and sweat glands.
In the case of Frey syndrome, clinical findings are presumed to be due to injury or aberration associated with the autonomic component of the ATN. During healing, nerve fibres intended for the parotid may be misdirected and feed the sympathetic nerve fibres, which innervate the sweat glands and small blood vessels, explaining the erythema and hyperhidrosis seen in response to gustatory stimuli.
In adults, Frey syndrome is most commonly seen following obvious trauma such as surgery due to parotid or cerebellopontine angle tumour disease, cervical sympathectomies or radical neck dissections. In children, the incidence of Frey syndrome is low, but this is likely due to under-reporting and under-recognition of cases.
In some cases, there is history of local trauma in the parotid area, most commonly at birth, although reports of accidental trauma later in life causing Frey syndrome have been reported.
Frey syndrome usually manifests in early infancy following exposure to solid foods. Vigorous chewing elicits a stronger stimulation of the parotid glands. The erythema typically begins shortly after mastication of food and lasts for 15 min to 45 min. It is not accompanied by discomfort, itching or burning. In contrast to adults, hyperhidrosis does not usually occur in children with Frey syndrome, possibly due to the immaturity of their sweat glands.
Because of the development of symptoms after eating, many patients are initially suspected of having a food allergy. Frey syndrome may be mistaken for food-induced allergic cutaneous reactions such as oral allergy syndrome, acute urticaria and allergic contact dermatitis. However, there are distinguishing features.
In oral allergy syndrome, patients typically experience itching and swelling of the lips and face following ingestion of certain foods, including apples, peaches, nuts and certain raw vegetables. Acute urticaria and allergic contact dermatitis are also pruritic.
In Frey syndrome, the gustatory flushing is benign and nonprogressive. No specific treatments are necessary in affected children, and the flushing disappears spontaneously with time. However, recognition of the process is important to avoid mislabelling of children as having a food allergy or subjecting them to unnecessary laboratory testing.