Definition: Oral allergy syndrome, or more recently called pollen-food allergy syndrome (PFAS), is a relatively common form of food allergy. It occurs in people who have pollen allergy, although not all patients have obvious hay fever or seasonal allergy symptoms. Patients typically report itching and/or mild swelling of the mouth and throat in 5 to 10 minutes following ingestion of certain uncooked fruits, raw vegetables or nuts. The symptoms result from contact urticaria in the oropharynx caused by pollen-related proteins in these foods. A small proportion of affected individuals experience systemic allergic reactions, although the disorder must be differentiated from more serious forms of food allergy.
Systemic reactions: Fewer than 10 percent of patients with allergies to fresh fruits and vegetables experience systemic symptoms. Ingestion of large quantities of the raw plant foods tends to be associated with more severe symptoms, including anaphylactic shock (1.7%). True systemic reactions involve tissues that do not come into direct contact with undigested food. Symptoms may include the entire range of IgE-mediated allergic manifestations, such as urticaria, angioedema, nasal congestion, sneezing, flushing, wheezing, cough, diarrhea, and hypotension.
Local reactions: A small percentage of patients complain of nausea and abdominal discomfort, which may represent esophageal and gastric symptoms that develop before the allergen is fully degraded. Some individuals develop analogous contact urticaria on their hands after handling raw vegetables. These two presentations are better classified as local reactions.
Natural history: PFAS can develop in childhood or adulthood. Usually, patients develop allergic rhinitis to pollen first and then develop PFAS following an increase in the severity of allergic rhinitis. However, PFAS is occasionally the first manifestation with no or minimal allergic rhinitis symptoms reported by the patient. When PFAS develops in a child, the number of foods that cause symptoms tends to increase over time. Some adults with pollen allergy also progress to experiencing PFAS to an increasing number of plant foods. PFAS tends to be a persistent condition that is lifelong, unless the patient undergoes immunotherapy for treatment of the underlying pollen allergy, and this is only successful in controlling symptoms of PFAS in a subset of patients.
Forms of foods: In most cases, symptoms only develop in response to eating the raw, uncooked food. Some patients react predominantly to the peel of the raw fruit or vegetable and tolerate pulp. Patients usually tolerate the culprit food in various cooked forms. Cooking, baking, or even briefly microwaving raw fruits and vegetables is usually sufficient to alter the allergens that are responsible for PFAS. Tree nuts and peanuts are an important exception to this generalization, as roasted nuts can cause PFAS.
Avoidance: Dietary avoidance of the offending plant foods, in the form in which it causes symptoms, is the most common approach to management. However, strict avoidance may not be uniformly necessary if symptoms are mild. Additionally, patients may continue to eat forms of the foods that do not cause symptoms. Cooked, processed, and sometimes frozen forms of the foods typically do not cause symptoms of PFAS.
Indications for epinephrine: Practices regarding prescribing epinephrine auto injectors vary among allergists and the patients need to discuss in more details about this with their allergists at Allergy Partners
Immunotherapy: In some studies, subcutaneous immunotherapy (SCIT) induced a significant or total disappearance of PFAS symptoms and reduced skin reactivity. In contrast, none in the control group experienced decreased symptoms or reduced skin reactivity. Our clinical experience also confirms that most patients with PFAS could tolerate many foods after they have built SCIT to their maintenance dose. However, other studies did not show significant improvement after SCIT.
Oral immunotherapy with food: The question of whether it is possible to induce oral tolerance in patients with PFAS by repeatedly ingesting the causative food was addressed in a randomized, controlled trial of 40 adults. Seventeen of 27 patients (63%) in the active group could tolerate a whole apple by the end of the study, compared with 0 of 13 patients in the control group. This approach appears to be effective in a subset of patients, but requires ongoing exposure once tolerance is induced.
Allergy Partners is the nation’s largest allergy and asthma practice, with locations across 23 states. As the leaders in allergy and asthma care, Allergy Partners provides patients with high quality, evidenced based and cost-effective care.
Shanze (Sam) Wang, MD, PhD
Allergy Partners of Albuquerque
Clinical manifestations and diagnosis of oral allergy syndrome (pollen-food allergy syndrome)Nowak-Wegrzyn, A. Clinical manifestations and diagnosis of oral allergy syndrome (pollen food allergy syndrome). UpToDate. May 2017
Nowak-Wegrzyn, A. Management and prognosis of oral allergy syndrome (pollen food allergy syndrome). UpToDate. May 2017
Management and prognosis of oral allergy syndrome (pollen-food allergy syndrome)Clinical manifestations and diagnosis of oral allergy syndrome (pollen-food allergy syndrome)Clinical manifestations and diagnosis of oral allergy syndrome (pollen-food allergy syndrome)Clinical manifestations and diagnosis of oral allergy syndrome (pollen-food allergy syndrome)Clinical manifestations and diagnosis of oral allergy syndrome (pollen-food allergy syndrome)Clinical manifestations and diagnosis of oral allergy syndrome (pollen-food allergy syndrome)