Oral Allergy Syndrome. Clinical Manifestations of Food Allergy

Tuesday, September 2nd, 2014 No Commented
Categorized Under: Allergies

Oropharyngeal symptoms may be isolated or part of a systemic IgE-mediated food-allergic reaction. These symptoms often present quickly due to direct contact of the allergen with the oropharyngeal mucosa after ingestion. When oropharyngeal symptoms present alone, potential reasons may include that the underlying food
Clinical Manifestations of Food Allergy
allergy is mild, a low dose of food allergen was ingested, or the food allergen is labile, as is the case with oral allergy syndrome (OAS).
OAS, also referred to as pollen-associated food allergy syndrome, is a form of IgE-mediated food allergy characterized by immediate pruritus; tingling; or mild swelling of the lips, tongue, palate, and throat after eating certain raw fruits and vegetables.22 It affects up to half of pollen-allergic patients. The underlying mechanism involves heat-labile food proteins of plant origin, which are structurally similar and thereby cross-reactive with pollen allergens. For example, an individual with birch tree pollen allergy may experience these oropharyngeal symptoms upon eating fresh apple, pear, and cherry, while a ragweed-allergic patient may develop symptoms after eating melons and banana. The causative fruits and vegetables can usually be tolerated in cooked or heated forms due to the heat-labile nature of the proteins.
Case Study
A 35-year-old male reports that he develops itching of his mouth and throat whenever he eats raw apples, especially during the early spring. His symptoms have never been more severe or widespread than oropharyngeal itching, but he worries whether they can become more serious in the future and whether he needs to carry an epinephrine autoinjector. What advice would you give him? These symptoms are consistent with OAS in a birch-allergic individual. It is common that symptoms are more prominent during the relevant pollen season. OAS typically causes a mild localized reaction limited to the oropharynx, which subsides within minutes of ingestion. Less than 10% of patients experience more systemic symptoms, and only 1% to 2% progress to anaphylaxis.23 In the absence of any prior systemic reactions after apple ingestion, epinephrine would not be indicated.