That new or worsening allergic tickle or itch in your mouth after eating things like avocado, apple, Indian food, or even drinking high-quality nut milk is definitely not in your imagination. You may have started avoiding these foods and others entirely to avoid the uncomfortable symptoms and distress that it could spread further.  


Oral Allergy Syndrome (OAS) or pollen-food allergy syndrome, which better describes the underlying nature of the “allergic reaction”-like symptoms in your mouth, is confusing in many ways. This syndrome is not a true allergy but caused by a cross-reactivity between proteins found in edible plants and pollen from closely related trees, grasses, and weeds. 


For a Table of pollen and cross-reacting foods, visit the American Academy of Allergy Asthma & Immunology.


Molecular mimicry: When allergies go south

These proteins are recognized as antigens, a foreign and potentially toxic substance, by your immune system and a chain reaction ensues. After consuming certain fruits, vegetables, spices, nuts, seeds, and legumes, your immune system mounts a response due to structural similarities between antigens in food that you eat and antigens in pollen that you inhale, to which you are actually allergic. The most common offenders are birch, alder, ragweed, mugwort, Timothy and orchard grass. Subsequently, the release of antibodies and activation of mast cells in local tissues that have come in contact with said antigens will produce local symptoms.  


Distinguishing OAS from more serious allergies

While the onset of symptoms can be swift like in anaphylactic reaction, the itching, tingling, swelling or hives are usually relatively mild, limited to the oral cavity (lips, tongue, gums, and throat) or face, and specifically affect those with seasonal allergies (hayfever). Both OAS and anaphylaxis are Type I hypersensitivity, IgE-mediated immune responses, of which there are two classifications. Seasonal allergies sufferers can develop OAS later in life with repeat sensitization to pollen. You can grow into OAS (Class 2) “food allergies” after adolescence, but you can grow out of true (Class I) food allergies from childhood. Only rarely does OAS progress into anaphylaxis with severe throat swelling and difficulty swallowing or breathing. 


When natures puts it in a nutshell 

Since nuts, legumes, whole spices, and seeds–whether eaten alone or within countless fruits and vegetables–contain the genetic material for propagation, they are inherently resistant to plant diseases and environmental changes that would impact their survival. This presents a challenge for the basic digestive enzymes found in your saliva, which specialize in breaking down starch and fat not protein. Still, the symptoms of OAS usually resolve within 30 minutes, once the immune complexes are cleared. The severity of OAS and actual food allergies is largely determined by the stability of the allergen. Some food proteins can even survive the extreme temperatures of freezing, cooking, and pasteurization. 


Confusion around language for food-related symptoms

Food allergies, food sensitivities, and food intolerances are separate things that need to be managed differently. The terms are often used interchangeably in the mistaken belief that they collectively describe the same thing: any unpleasant bodily response after eating, when in fact, food intolerances are a result of an enzyme deficiency and not immune-mediated. To complicate matters, Oral Allergy Syndrome also involves environmental allergies, which change more seasonally than most of our diets these days. OAS is probably the most common food-related allergic condition in adults with more than 60% of food allergies attributed to the aforementioned cross-reactions. 


Managing OAS

If you suspect you have OAS and have not already done so, you may want to consider a skin allergy or blood test to check for allergies to the common pollen triggers. It is also a good idea to further evaluate any reactions to peanuts as there is a higher risk of symptoms turning serious and sensitization to related foods such as legumes, soy, and tree nuts. Avoidance of known cross-reactive foods, especially raw or with the skin / peel, during periods when seasonal allergies heighten can help reduce symptoms. Soaking and sprouting nuts, seeds, and legumes may lessen the impact as well. Treatment options include antihistamines, allergy shots, and desensitization therapy (local honey, sublingual immunotherapy (SLIT)) as well as the following, which are available through Brio:  acupuncture, Bowen Therapy, and low level laser / phototherapy!


The term Oral Allergy Syndrome can be a mouthful both literally and figuratively. Thankfully symptoms are self-resolving and most times it is not difficult to swallow (or live with). Addressing the underlying seasonal allergies and being mindful or what, when, and how you eat certain foods are important components of any management strategy.


In Health,
Dr. Vanessa