An 8-month-old boy arrived at a Canadian allergy clinic carrying a long list of suspects: milk, soy, peanut, wheat, and egg. His parents had watched his face turn red within seconds of feeding, again and again. Several emergency department visits had hardened the fear that something in his diet was dangerous, and his menu kept shrinking.
The cause had nothing to do with his immune system. It was a nerve on the right side of his face that had rewired itself to the wrong destination.
Allergists at Western University in London, Ontario, described the case in Allergy, Asthma & Clinical Immunology on Feb. 15, 2026. Melanie Semaan, Sheikha Alkhuder and Samira Jeimy diagnosed Frey's syndrome, a benign condition in which eating triggers flushing, and sometimes sweating, on one side of the face instead of ordinary salivation.
One Cheek, Never Two
The referral described immediate facial "hives" after feeding. On careful reassessment, the reactions looked nothing like what that word implies. The episodes consisted of flushing and sweating only. There was no swelling, no wheezing, no vomiting, no hives anywhere on the body. They were reproducible, but they happened with many foods, including ones that are not common allergens.
Skin prick testing and blood tests for food-specific IgE antibodies to milk, egg, peanut, soy and wheat all came back negative.
Because the family remained worried and the original history was muddled, the team ran a supervised baked milk oral food challenge in clinic. Within 10 minutes of eating, the boy developed isolated redness and sweating on his right cheek. Nothing else happened, and the reaction faded on its own with no treatment. A video the family had recorded at home during a formula feeding showed the same one-sided pattern.
That combination settled the diagnosis: a fixed distribution on one side, reproducibility across unrelated foods, no systemic involvement, and negative allergy testing. The dietary restrictions were lifted.
Crossed Wires Along the Auriculotemporal Nerve
Frey syndrome takes its name from Łucja Frey, the Polish neurologist who characterized it in 1923, although physicians had described the pattern as far back as the 18th century. In adults, it most often follows surgery near the parotid glands, the largest salivary glands in the body, which sit just below the ears.
The mechanism is a wiring error. Parasympathetic fibers that normally drive the parotid gland get injured, and as they regrow, they end up connected to sympathetic pathways that supply blood vessels and sweat glands in the skin near the ear and temple. After that, a taste stimulus that should produce saliva produces a flush instead.
In infants, the injury is often obstetric. A 2022 systematic review in the European Journal of Pediatrics pooled 121 cases of Frey syndrome unrelated to surgery or diabetes. Symptoms began at age 18 or younger in 113 of them, or 93 percent. The reaction was one-sided in 83 percent. A forceps birth was the single most common identifiable cause, present in 52 percent. In 36 cases, no cause was ever found.
The review also catalogued what these children never had. Reddening in front of the ear appeared in all 121 cases. Welts, itching, scratch marks, and any sign of multi-organ involvement were reported in none of them. Sweating, local warmth, and general discomfort turned up only in a minority and were significantly less common in the pediatric cases than in the adult ones, which is one reason the sweating in this 8-month-old was a useful clue rather than a typical feature.
The Ontario case is not the first of its kind. A 1997 series in Archives of Dermatology described eight infants with localized facial flushing, frequently with a history of perinatal trauma. A later report in BJGP Open followed a child through allergy testing before the correct answer emerged. And in April 2026, a Japanese team published an unusual bilateral case in an infant born with no history of instrumental delivery.
The Real Cost of Calling It an Allergy
That same review found the diagnosis took a year or more in 45 percent of cases, and that an allergy evaluation had been performed in roughly half.
The Western University team argues that misclassification is not harmless. Infants placed on elimination diets risk inadequate nutrition and slowed growth. Cutting out common allergens may also interrupt the process by which a young immune system learns to tolerate those foods, which can make a genuine allergy more likely rather than less. Families absorb repeated emergency visits and sustained anxiety around every meal.
Once the condition is recognized, management is straightforward. Frey's syndrome in infancy is benign, usually improves or resolves as the child grows, and typically requires no referral to neurology or otolaryngology. The treatment, in effect, is an accurate explanation.
What This Case Does Not Say
A single case report cannot establish how often feeding-related flushing in infants is Frey's syndrome rather than allergy, and no parent should try to sort the two out at home. Facial redness during eating that comes with hives, lip or tongue swelling, coughing, wheezing, repeated vomiting or floppiness is a medical emergency and should be treated as one.
What the report does offer is a set of features worth flagging to a clinician: redness confined to one cheek in the same place every time, sweating rather than welts, no other symptoms, and the same reaction across foods that have nothing in common. The authors single out the home video as one of the most useful pieces of evidence they had, because it captured what a clinic visit could not.
Anyone whose child has been placed on a restrictive diet for suspected food allergy without confirmatory testing should ask a pediatrician or allergist whether formal evaluation is warranted before more foods come off the list.
Key Questions Answered
What is Frey's syndrome?
It is a nerve condition, also called auriculotemporal syndrome, in which eating triggers flushing and sometimes sweating on one side of the face. It happens when parasympathetic nerve fibers meant for the salivary gland regrow into pathways serving skin blood vessels and sweat glands.
How did doctors tell it apart from a food allergy?
The reaction was confined to the right cheek, involved no hives or systemic symptoms, occurred with many unrelated foods, and all allergy testing was negative. A supervised baked milk challenge reproduced the flushing without any allergic features.
Is it dangerous?
No. The condition is benign and often improves or resolves on its own as a child gets older. Management is reassurance rather than medication or surgery.
What causes it in babies?
In the largest pooled review of non-surgical cases, a forceps birth was the most common identifiable cause, found in 52 percent of patients. In many cases, no cause is ever identified.
Why does a wrong diagnosis matter?
Unnecessary elimination diets can compromise a growing infant's nutrition, and avoiding common allergens may interfere with the development of oral tolerance, potentially increasing the risk of true allergy later.
When should facial redness during feeding be treated as an emergency?
Any time it comes with hives, swelling of the lips or tongue, breathing trouble, repeated vomiting or lethargy. Those are signs of a systemic allergic reaction and require immediate medical attention.
