Oral Allergy Syndrome: Symptoms, Diagnosis, Triggers, and Treatment

Oral allergy syndrome (OAS) affects as many as 10 percent of the global population. While OAS rarely affects young children, it is most commonly seen in older children and adults with environmental allergies. Also called pollen-food syndrome, OAS is a type of food allergy triggered by raw forms of fruits, vegetables, nuts, legumes, seeds, and even certain spices.

OAS is a secondary allergy, meaning that those who have oral allergy syndrome also suffer from environmental allergies such as pollen and dust mite allergies, and occurs because of a cross-reaction between pollen or dust mite proteins and similarly structured proteins in fruits and vegetables. In OAS, the immune system misidentifies food proteins as pollen or dust mite proteins, resulting in an allergic reaction. 

The most common pollen allergies connected to oral allergy syndrome include: alder, birch, grass, mugwort, and ragweed. While oral allergy syndrome is due to an inhaled environmental  allergen, OAS can be misdiagnosed as a true food allergy. Before pursuing treatment, it is important to determine whether you are suffering from cross-reactivity between an environmental allergy and a food, or a true food allergy.

Symptoms of an Oral Allergy Syndrome Reaction

While symptoms can certainly be uncomfortable, OAS is not considered a life-threatening allergy. Reactions typically last a matter of minutes to an hour. Symptoms of an oral allergy syndrome reaction include: 

    • Tingling and itching in the mouth, throat, and lips
    • A scratchy sensation, tightness in the throat
    • Lip swelling or numbness

Oral allergy syndrome symptoms may be exacerbated by exercising or consuming alcohol directly after coming into contact with an allergen. 

In extremely rare cases (1.7 percent of patients), anaphylaxis may occur — a severe allergic reaction that can become life-threatening without immediate treatment. If you have a history of severe reactions, discuss an emergency anaphylaxis plan with an expert clinician. 

Oral Allergy Syndrome Testing and Diagnosis

In cases of suspected oral allergy syndrome, it is important to distinguish between a true food allergy and an allergic reaction caused by pollen or dust mite cross-reactivity. There are four ways to clinically determine whether someone has a true food allergy. These include: 

Skin Prick Test

This is a safe and low-risk test in which the skin is lightly pricked with a suspected allergen. Any skin reactions are closely observed and monitored by a clinician. Skin testing for environmental allergies is also helpful when distinguishing between OAS and a confirmed food allergy diagnosis. 

Blood Test

A blood test will measure the amounts of IgE antibodies that the immune system has deployed as a response to food-based proteins. Once drawn, the blood is sent to a lab to be evaluated. Blood tests are safe for adults as well as infants and children. While the results of a skin prick test are immediate, the results from a blood test often take a few days. 

Component Test

A component test is a form of a blood test that assesses whether a patient can tolerate certain components of nuts. This test provides heightened clarity to a clinician and pinpoints specific aspects that may be less harmful. 

Oral Food Challenge

This test is particularly useful as the final step in determining whether a food allergy has been outgrown, or when skin and blood tests are inconclusive. An oral food challenge can also determine, with certainty, whether raw fruits and vegetables may safely be consumed. This step is only taken after a full review of patient history and only in cases where a clinician determines that a patient is likely to pass. 

Under close supervision and observation, the patient will consume very small amounts of suspected allergens in increasing amounts over a three to four hour time period.

Ingredients that Can Trigger Symptoms of Oral Allergy Syndrome 

Oral allergy syndrome is caused by cross-reacting allergens found in pollen and fresh fruit, vegetables, nuts and other foods. The body’s immune system recognizes the pollen and similar proteins found in the food and reacts with an allergic response. Every patient is unique, and may experience adverse reactions to different types of foods.

Common fruit triggers of OAS include: 

    • Apples
    • Apricots
    • Bananas
    • Cantaloupe
    • Cherries
    • Honeydew
    • Kiwi
    • Mango
    • Nectarines
    • Oranges
    • Peaches
    • Pears
    • Plums
    • Tomatoes
    • Watermelon

Common vegetables and spices that contribute to OAS include: 

    • Carrots
    • Celery 
    • Cilantro 
    • Coriander 
    • Cucumbers
    • Cumin
    • Dill
    • Fennel
    • Green peppers
    • Parsley
    • Parsnip
    • Peas
    • Potatoes
    • Squash
    • Zucchini 

Those with OAS may be advised  to avoid the following raw nuts, seeds, and legumes

    • Almonds
    • Beans
    • Hazelnuts
    • Lentils
    • Peanuts
    • Sunflower seeds
    • Walnuts

The American Academy of Allergy Asthma & Immunology has a useful summary chart of OAS pollens and cross reacting foods that can be printed out.

Reducing Symptoms of Oral Allergy Syndrome 

In some cases, you may be able to tolerate a certain food once it is prepared. Heating, cooking, or peeling vegetables and fruits can often allow allergens to be safely consumed. Similarly, opting for canned fruits and vegetables may eliminate OAS symptoms. For example, if your oral allergy syndrome is triggered by raw tomatoes, you may be able to eat tomato-based sauces without symptoms. 

But while the vast majority of triggers for oral allergy syndrome consist of the food itself (i.e., tomatoes, apples, cilantro, zucchini), others can be more challenging to identify. Those with oral allergy syndrome should have a comprehensive understanding of what foods cause symptoms. Ultimately, it’s important to share the list of identified triggers with an allergist and work together to understand the root causes and what foods to watch out for. 

Oral Allergy Syndrome Treatment Options

If oral allergy syndrome is linked to a certain type of inhaled allergen — pollen or dust mites —  treating the environmental allergy may relieve symptoms. This may include antihistamines, or seasonal allergy shots. Our skilled allergists will carefully examine your medical history, symptoms, and allergic reactions to determine the best treatment approach. 

In cases where the diagnosis is a true food allergy, patients can be successfully treated with oral immunotherapy (OIT). Research shows that OIT is safe and effective in treating food allergies for patients of all ages. 

Oral immunotherapy desensitizes the body to a food allergen, gradually introducing small amounts of proteins over time and retraining the immune system. At Latitude Food Allergy Care, oral immunotherapy is offered for single or multiple food allergens.

Decreased sensitivity to triggering foods creates a safeguard against accidental exposure, decreases food-based anxiety, and empowers patients with greater dietary flexibility. As a result, patients who undergo OIT often experience drastic improvements in overall quality of life. OIT is approximately 85 percent effective when performed by a skilled clinician who specializes in food allergen treatment. 

Do you suspect that you or someone you love may have oral allergy syndrome? Take the next step toward better health and better quality of life with Latitude Food Allergy Care. Contact us today to schedule your no-obligation call with one of our Patient Care Coordinators to discuss whether you may be a candidate for oral immunotherapy treatment.

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