Diseases and Conditions

Oral Allergy Syndrome

When reviewing a client’s medical history, you see an extensive list of food allergies, including certain raw fruits and vegetables. The client indicates that they can safely consume these foods when cooked. You make a note to clarify this with them in person; surely this is a food preference or a digestive issue, and not a true allergy, you think to yourself. Unlike harmful bacteria, a food allergen can’t be cooked out of a food—at least that’s what you’ve been taught.

But what if this isn’t always the case? Those living with oral allergy syndrome (OAS) may identify as having a food allergy, except, in this case, the allergen can be cooked out for safe consumption. It’s important to understand the distinction between a food allergy and OAS to best serve these clients.

Food Allergies
More than 32 million Americans are living with potentially life-threatening food allergies, and incidence is on the rise. Figures from Food Allergy Research & Education (FARE)—the leading organization for food allergy research—show a 377% increase in private insurance claims for food-related anaphylaxis between 2007 and 2016.

Food allergies pose a uniquely dangerous situation for those who live with them; the only treatment is complete avoidance of the offending allergen, but food is essential and can’t be avoided altogether. As RDs know, those living with a food allergy must be vigilant about reading labels and ensuring that their food is always prepared appropriately with the avoidance of cross-contact.

An allergic reaction happens as an inappropriate immune response to a protein in a food. A person can have an allergic reaction to any food; however, in the United States, there are eight allergens that account for 90% of the most severe food allergy reactions: milk, egg, soy, wheat, fish, shellfish, peanuts, and tree nuts. The FDA requires these allergens to be listed in ingredient statements by common name, which makes it easier—but by no means easy—to identify these items in food products.

FARE has numerous resources for people living with food allergies and those in their lives. Absent, however, is information about OAS. That’s because although people living with OAS often describe it as a food allergy, it’s not a true food allergy—it’s a contact allergy that occurs due to a protein found in fresh fruits and vegetables that’s structurally similar to a protein found in pollen.

A person with a pollen allergy has an increased likelihood of also having an allergy to fresh fruits and vegetables that are within the same botanical family as the plants to which they’re allergic. For example, someone allergic to birch pollen might have cross-reactivity to apples, pitted fruits, kiwi, carrots, celery, parsley, nuts, and legumes—or to any combination of these. The American Academy of Allergy Asthma & Immunology has a helpful chart to refer to of pollens and cross-reacting foods.

Biologically, OAS is more akin to a seasonal allergy than it is to a food allergy, except in the potential severity of the reaction. In contrast to food allergies, OAS symptoms usually are centered around the mouth—itching, tingling, or swelling of the mouth, tongue, lips, and throat; nasal congestion and sneezing; and lightheadedness. Up to 2% of people with OAS have severe oral reactions, while up to 9% have severe systemic reactions, as with a food allergy. In both cases, life-saving epinephrine and a hospital visit may be required. In all cases, the offending food should be avoided in its raw form.

The RD’s Role
Chances are you’ve come across someone with OAS in your practice as an RD, and it’s important to know how to help these clients. Being aware of OAS and its symptoms can help identify those living with it; many people with OAS may have self-diagnosed a food allergy and are unnecessarily avoiding a food or food group entirely. We have a responsibility to refer these clients to their doctor for an official diagnosis and to help them follow up on any recommendations or treatment plans. If their OAS is severe enough, they may need to have an epinephrine pen prescribed and it’s important to review emergency planning with them.

Unlike with true food allergies, the allergenic produce still can be safely eaten by someone who has had an allergic reaction to it in the past. Cooking the fruit or vegetable changes the structure of the protein, making it safe to eat. A person with OAS also can safely consume canned fruits and vegetables and sometimes can even eat the fruit or vegetable raw if they don’t eat the skin, where the concentration of the allergenic protein is the highest. If they do have symptoms of an allergic reaction while consuming fruits and vegetables in these ways, they should be referred to their doctor, as another condition may be present.

Lastly, having an allergic reaction is scary. It’s important to teach people living with OAS that although they may need to avoid certain foods, they still can follow a healthful eating pattern and don’t need to fear food. Help them learn about substitutes for their favorite recipes that include these foods, and, if their allergy is severe and requires them to avoid several foods, teach them about foods that are nutritionally equivalent. Living with a food allergy or OAS can be challenging, but the right team—one that includes an RD—can make it easier.

— Kim Crudele, RDN, is a New Jersey–based dietitian specializing in school nutrition and nutrition communications. She’s the owner of Well Balanced RD, where she does school and corporate wellness consulting. Kim is also a freelance writer concentrating on food, nutrition, health, and agriculture. She’s an avid gardener with dreams of starting her own CSA, a distance runner, and a dog lover. She’s currently pursuing her MA in communications at Northern Arizona University.

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