From Pollen to Plate: Identifying Pollen Food Allergy Syndrome

Despite affecting up to 70% of pollen-allergic individuals, pollen-food allergy syndrome (PFAS) is an under-recognized condition. The condition is caused by cross-reactivity, which is when patients’ bodies recognize proteins in one substance, such as pollen, as being similar to proteins found in another substance, like foods. Patients with pollen protein allergies may react when they encounter a comparably shaped protein, known as Class 2 allergens, in food. These proteins break down when heated or during digestion, so they may cause itchiness or swelling of the mouth, face, lip, tongue and throat immediately after eating plant foods such as fruits, vegetables, nuts, and legumes – a reaction called PFAS.

Diagnosing PFAS can be challenging, but establishing a thorough symptom history along with specific IgE blood testing can build a fuller picture of patients’ allergic triggers and sensitizations, helping clinicians develop accurate, tailored treatment recommendations and ultimately improve their patients’ quality of life. 

Understanding PFAS and its pervasiveness

While prevalence numbers vary, PFAS is not uncommon. It’s estimated that over 60% of food allergies are cross-reactions between food and inhaled allergens. Up to 20% of children and up to 58% of adults will have this condition, and allergies to different pollens can result in different cross-reactivities. For example, patients with a birch pollen allergy may have a reaction when eating foods like peaches, apples, peanuts, hazelnuts, soy and celery, whereas patients with grass and weed pollen allergies may experience a reaction when eating melons, oranges, tomatoes, cucumbers, bananas, and certain spices. The prevalence of PFAS also varies by geography, as the different specific pollen types, which are distributed in specific areas, trigger the condition.

Certain plant families have similar-shaped proteins that cause cross-reactivity, making it vital to understand if patients are sensitized to certain pollens. When patients are allergic to pollen and have respiratory symptoms, there are certain proteins that cause the symptoms to which they develop antibodies. When these patients are exposed to those specific allergens in certain plant foods, these similar shaped proteins cause the patient’s body to recognize it similar to the pollen allergen. This then causes a reaction, but because the allergen is ingested rather than inhaled, the patient has a reaction more consistent with food allergy symptoms than respiratory symptoms.

The proteins that are responsible for the food pollen allergy syndrome are typically labile proteins, meaning that they are heat and digestion sensitive and typically get denatured either by digestion in the gut, heating, or peeling the outer layer of the food, as some of the allergens are concentrated in the peel.

PFAS symptoms are generally mild, but, while uncommon, systemic reactions can occur when patients overwhelm their body’s ability to denature the protein. These reactions, which can include nausea, abdominal discomfort, diarrhea, rhinitis, difficulty in breathing, skin rash, urticaria-angioedema or hypotension, and anaphylaxis, have been reported in 2-10% of cases. Regardless of whether a patient experiences minor symptoms or severe systemic reactions, early and accurate diagnosis remains the cornerstone of effective management and prevention of allergic reactions.

The importance of patient history in diagnosing PFAS 

When patients present with isolated oropharyngeal and upper gastrointestinal tract symptoms after consuming plant foods, it’s a great opportunity for a full allergy assessment of the patient, starting with the most important test – an allergy focused clinical history.  If seasonal respiratory allergy symptoms are present, then a comprehensive respiratory allergen sensitization profile specific to the patient’s geography will help in confirming pollen and other environmental allergies and inform a personalized management plan that includes appropriate therapeutics and environmental mitigation strategies to reduce exposure to identified aeroallergens.  Assessment of suspected food allergies should be completed with specific IgE allergen sensitization testing that is targeted to the suspected allergens identified in the patient’s clinical history. If available, testing which includes automatic reflexing to allergen components of that food should be selected to provide the most comprehensive information about potential allergenic protein triggers that patients may be sensitized to.  This information can help to identify primary allergy, cross-reactivity, and even the potential risk of systemic reactions.  

For patients, getting the correct diagnosis, whether it’s a food allergy, pollen allergy, or both, leads to better informed management advice. From environmental exposure reduction for identified aeroallergens or specific advice that can include peeling and / or heating fruits and vegetables prior to consuming, being cautious with the consumption of certain foods during peak pollen seasons or avoiding some foods altogether.  Diagnostic testing for sensitization to suspected allergens allows clinicians to provide personalized, preventative strategies to allow patients to minimize symptoms and avoid high risk situations.  

Determining the root cause of allergies to lead a healthier life

Because up to 80% of allergy patients are allergic to more than one thing and allergens are additive, it is critical to have an understanding of what allergens the patient is sensitized to and that are contributing to their cumulative threshold. While they may have PFAS, they may also have one or more primary food allergies, so a comprehensive assessment is important to help them address their symptoms from a preventative medicine standpoint. 

Prioritizing early and accurate allergy diagnosis can help patients avoid unnecessary exposure to allergens and proactively address their symptoms. With PFAS, taking the right diagnostic approach ultimately shifts allergy management from reactive to proactive, ensuring better care, reducing allergen exposure, and improving quality of life for patients.

Photo: fcafotodigital, Getty Images

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