Those who suffer from oral allergy syndrome (OAS), also known as “pollen food syndrome” and "inhalant-food cross-reactivity," have difficulty eating certain fresh fruits and vegetables when seasonal pollen allergies to plants like ragweed and especially birch, are triggered. According to the American Academy of Allergy Asthma & Immunology (AAAAI) about a third of people with seasonal allergies may suffer from OAS, which results from a cross reactivity between seasonal airborne pollen proteins and similar proteins found in some foods.
How OAS Works
People who are allergic to birch and grass pollens have a 35% chance of experiencing cross reactivity symptoms to certain foods. ["Oral Allergy Syndrome." 2006. Allergy New Zealand. 21 Oct 2008]. OAS is an “incomplete food allergy,” distinct from complete food allergies , which are caused by an immune system response to food proteins.
The proteins that trigger oral allergy syndrome, unlike those that provoke complete food allergies, are broken down by cooking and digestion, so many OAS sufferers can actually eat cooked or processed versions of the foods that cause oral allergy symptoms in their raw form. This is also why incomplete food allergy symptoms are mostly oral in nature, causing itching of the mouth, tongue and throat. [Yagami, Takeshi. "Allergies to cross-reactive plant proteins. Latex-fruit syndrome is comparable with pollen-food allergy syndrome." International Archives of Allergy and Immunology . 128.4 (2002): 271-279. ] Also unlike complete food allergies, those who experience OAS typically don’t need to avoid all the foods that can cause it, but only those to which they’ve experienced a reaction.
Oral allergy syndrome symptoms are usually mild, typically identified by an itching or tingling sensation in the mouth and tongue upon eating certain fresh fruits and vegetables. More extensive reactions can include swelling of the mouth, face, tongue and throat. OAS symptoms are usually worsen during a particular pollen allergy season, but can occur at any time of the year.
OAS Triggers and their Sources
Foods which may cause OAS to develop vary by pollen trigger. Allergy to birch pollen produces the most oral allergy cross-reactivity symptoms, to foods in these plant families:
- apple family, which also includes pears;
- plum family, including almonds, apricots, cherry; nectarine, peach, and prune;
- parsley family, which includes carrots, celery; fennel, and parsnip and
- walnuts.
Ragweed pollen allergy can trigger oral allergy reactions to bananas and melons. And grass pollen allergy can produces OAS to melons, kiwis, oranges, and tomatoes.
Managing OAS
Treating OAS is mostly a matter of responding to symptoms. According to the Calgary Allergy Network, the following should be done for OAS symptoms:
- As soon as oral itching and tingling symptoms occur, stop eating the food that triggered it.
- Antihistamines usually ameliorate reactions.
- Peeling a fruit or vegetable can help, as can sometimes briefly microwaving an offending food.
- Those who experience more severe reactions, like difficulty breathing, should consult with a doctor and always carry an injectable antihistamine like an EpiPen.
- If OAS causes reactions to nuts, all nuts, cooked or raw, should be completely avoided due to the more serious nature of nut allergies.
While those with grass and birch pollen allergies are a third more likely to experience oral allergy syndrome, it is a fairly easily managed allergy that can be ameliorated by avoiding or cooking the foods that cause oral allergy symptoms, and lessened with antihistamines.
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