An eight-month-old boy was referred to an allergy clinic with what his family described as immediate hives after milk, soy, peanut, wheat, and egg. There had been several emergency department visits. Foods were being dropped from his diet one after another, and feeding had become a source of real anxiety at home.
Every allergy test came back negative. When allergists watched the reaction happen under supervision, they saw something that does not belong to any food allergy: redness and sweating confined to the right cheek, and nothing else.
Emergency Visits, Five Foods Cut, and Every Test Coming Back Negative
The case, published in Allergy, Asthma and Clinical Immunology, was reported in February by Melanie Semaan, Sheikha Alkhuder and Samira Jeimy of the Division of Clinical Immunology and Allergy at Western University in London, Ontario.
On careful reassessment, the episodes turned out to consist of flushing and sweating. There was no swelling, no wheeze, no vomiting, no other systemic signs. The reactions were reproducible with feeding, but they happened with many different foods regardless of how allergenic those foods were.
Skin prick testing and blood tests for specific IgE to milk, egg, peanut, soy, and wheat were all negative. With the family still worried, the team ran a supervised baked milk oral food challenge. Within 10 minutes of eating, the boy developed isolated redness and sweating on the right cheek. No hives. No systemic features. It resolved on its own. A video the family had recorded at home during a bottle feed showed the same thing.
That was enough. The diagnosis was Frey syndrome, also called auriculotemporal syndrome. Dietary restrictions were lifted, and the parents were reassured.
Crossed Nerve Wiring Turns a Salivation Signal into Sweat
Frey syndrome is a wiring problem. Parasympathetic nerve fibers that normally tell the parotid salivary gland to produce saliva get injured, and as they regrow, they cross into sympathetic pathways serving the sweat glands and small blood vessels of the skin over the cheek and temple.
The result is that the signal to salivate arrives at the wrong destination. Taste or chewing triggers localized flushing and sweating instead of, or in addition to, saliva. Because the auriculotemporal nerve runs on one side of the face, the reaction is strictly one-sided, which is the single most useful clue at the bedside.
In adults, the condition is a well-recognized consequence of parotid gland surgery. In infants, it happens without any surgery at all. A 1997 case series in Archives of Dermatology described eight infants with localized facial flushing, often in the setting of birth-related trauma. A 2015 report described a nine-month-old whose symptoms surfaced as solid foods were introduced. A 2016 report described an infant repeatedly misdiagnosed with food allergy. A 2022 systematic review pulled together 121 cases unconnected to surgery or diabetes, which the Canadian team cites as evidence that pediatric presentations are a recognized pattern rather than isolated curiosities.
One Side of the Face Is the Clue That Separates This From Anaphylaxis
Food allergy is a frequent reason infants get referred to allergy clinics, and it is genuinely common. CDC data from the National Health Interview Survey put diagnosed food allergy at 5.8 percent of U.S. children aged 0 to 17 in 2021, and at 4.4 percent of those aged 0 to 5.
That prior probability is exactly what makes this trap work. Parents describing facial redness after eating frequently use the word hives, and the referral history inherits that word. The authors identify the core diagnostic pitfall as the assumption that any reproducible food-triggered reaction must be an allergy.
The distinguishing features they lay out are specific. IgE-mediated food allergy typically involves more than one organ system, producing urticaria, swelling, wheeze or vomiting, and usually shows positive sensitization testing. Frey syndrome is one-sided, limited to the skin, reproducible across foods of wildly different allergenic potential, and benign. In this case, watching the reaction happen in clinic and comparing it against a home video of the same reaction settled the question.
Cutting Foods Out Carries Its Own Risks for a Growing Infant
A wrong diagnosis here is not harmless. The authors point out that infants placed on elimination diets risk compromised nutrition and growth, and that avoiding common allergenic foods can paradoxically raise the odds of developing a real food allergy by interrupting the acquisition of oral tolerance. Families absorb ongoing anxiety and repeated health care visits along the way.
Management of infantile Frey syndrome is mostly the absence of management. Once identified, it does not typically require referral to otolaryngology or neurology. The condition is benign and often improves or resolves over time. The useful intervention is recognizing it, restoring the diet, and telling the family what they are looking at.
This is one case report, and it does not change any allergy guideline. What it offers clinicians is a pattern worth checking before a child's diet narrows: if the redness is on one side only, if there is no swelling or breathing difficulty, and if it happens with foods that share nothing in common, the diagnosis may not be allergy at all. Parents who have watched a child react to food should still have that child evaluated, since true food allergy can be dangerous and needs proper testing rather than guesswork.
Key Questions Answered
What is Frey syndrome? A condition in which nerves that normally trigger salivation instead trigger flushing and sweating on one side of the face during eating, because parasympathetic fibers have crossed into sympathetic sweat and blood vessel pathways.
How did doctors rule out food allergy in this infant? Skin prick and blood IgE tests to milk, egg, peanut, soy, and wheat were negative, and a supervised baked milk challenge reproduced only one-sided cheek redness and sweating with no systemic symptoms.
What is the giveaway that separates it from an allergic reaction? The reaction is strictly on one side of the face, involves only the skin, and occurs with many unrelated foods. Allergic reactions typically involve more than one organ system.
Why does a misdiagnosis matter? Unnecessary elimination diets can harm an infant's nutrition and growth, and avoiding allergenic foods may interfere with building oral tolerance, potentially increasing the risk of real allergy later.
Does this mean parents should ignore reactions to food? No. Real food allergy is common and can be life-threatening. Any suspected reaction should be assessed by a clinician, who can order proper testing rather than relying on trial and error at home.
