Oral Allergy Syndrome Due to a Hidden Allergen in Mojo

Oral Allergy Syndrome (OAS) is a specific type of allergic reaction that mainly occurs after the consumption of raw fruit, vegetables, and nuts.¹ In adults, OAS represents the most common allergic reaction to food, affecting patients with pollen sensitization due to homology between plant proteins.² It is a complex syndrome with diagnostic and therapeutic challenges, requiring comprehensive history taking and examination. We discuss a case of OAS following Mojo (sauce used in Cuban food) ingestion, the diagnostic challenge, and our approach for its management.

A 32-year-old man with a history of seasonal allergic rhinitis with sensitization to oak, cedar and birch presented to the Allergy department for evaluation of a possible allergic reaction following three episodes of intense pruritus of tongue, palate, cheeks, and lips. On all three occasions, symptoms started 10 to 20 minutes after eating a pork sandwich with Mojo at a local restaurant. The patient did not take any medication for his symptoms as these would resolve within 10–15 minutes on its own. He recalled having these symptoms only after eating the same type of sandwich from the same restaurant during Spring-Summer but presenting no symptoms if he ate the sandwich during Autumn-Winter or with similar sandwiches from alternative restaurants. He denied any history of food allergies. The patient was unable to identify other possible causes for his symptoms other than the sandwich.

Upon thorough history taking, we determined that the “Mojo” used on the specific sandwich was the main difference between that restaurant’s recipe and others’ with which the patient never had any symptoms. Mojo is prepared with several cooked ingredients (garlic, cumin, black pepper, oregano, unripe orange, and olive oil) boiling for 10–20 minutes. There were no commercial extracts available for Mojo. We performed prick-to-prick testing to pork, whole Mojo (from the same restaurant) and each of its ingredients along with commercially available aeroallergens (Figure 1). The test resulted positive for whole Mojo, ripe orange, cumin, cedar, and oak.

Figure 1:

A. Prick to prick with Mojo B. Aeroallergens and positive control

We then performed prick-to-prick tests with Mojo using undiluted Mojo and ten-fold dilutions (1:10; 1:100; 1:1,000; 1:10,000; 1:100,000 and 1:1,000,000) on five healthy subjects and the patient. All dilutions and undiluted mojo were negative in healthy subjects. The patient had a positive reaction to undiluted and 1:10 dilution.

We then performed an oral challenge where the patient ate same type of sandwich at the clinic under close surveillance. Within 10 minutes of ingestion, patient reported pruritus of the buccal mucosa, tongue, and lips. There was no urticaria, rashes, angioedema or evidence of other systemic IgE-mediated reactions. Further, Oral challenges for individual component of Mojo were done. Pruritus was noted with ingestion of orange juice, but not with cumin. Patient was advised to avoid ingestion of foods containing Mojo during spring-summer to prevent worsening symptoms with pollen peaks and to use oral antihistamines in case of same presentation.

Spices, like the ones used in Mojo, are used in a wide array of foods, and beverages and may act as “hidden” allergens. Citrus fruit allergy, as seen our patient (orange), is often associated with cross-reactivity and sensitization to other plants such as, birch or grass pollen.³ Symptoms of allergy to orange is mainly local unlike other food allergy which have more generalized symptoms such as vomiting, diarrhea and abdominal pain.³ During an acute episode, a physical examination may reveal angioedema as well as perioral urticarial eruptions.^1,4

There is no consensus on the recommendation of a specific method of prick testing for patients with allergic reactions to spices. Testing for spices is a challenge with a lack of reliable commercially available extracts, such that it becomes necessary to test these patients with fresh foods. For several years, the prick-to-prick testing for fresh produce has been shown to be a more reliable method than the commercial extracts.⁵ In contrast, skin prick test can be unreliable because the cross-reactive epitopes get denaturalized by the manufacturing process⁶ and this also possess the risk of provoking clinical reactions.⁷ Prick-to-prick testing with freshly prepared extracts is more sensitive in detecting allergen-specific IgE antibody.⁸ Oral provocation test can help confirm the presence of the disease. For an accurate diagnosis, patients should be advised to keep a diary of food consumption based on which determination of food challenge tests should be performed.

Patient education is the most effective long-term management of this condition. Patients and their families should be made aware and instructed to read food and beverage labels, where all ingredients of the food are mentioned. In situations of hidden allergens, as in our case, patients with OAS can be treated with a combination of allergen avoidance and pharmacotherapy (antihistamines). Patients with history of anaphylaxis should have an epinephrine auto injector with them at all times.