If you suffer from hay fever and you have experienced itchy mouth, palate, or scratchy throat after eating certain raw fruits and vegetables or tree nuts, you may have oral allergy syndrome (also known as pollen-food syndrome). Oral allergy syndrome (OAS) is caused by cross reacting allergens (proteins) found in both pollens and raw fruits, vegetables, and some nuts. As these food and pollen proteins are very similar in structure, our immune system recognizes them as identical and directs an allergic response against both of them.
Symptoms of oral allergy syndrome include itchy mouth, scratchy and itchy throat, swelling of lips, mouth, or tongue. Itchy ears have also been reported. These symptoms are usually confined to one area and do not normally progress beyond the mouth. Because the symptoms are due to heat labile allergens in these foods, cooking the foods will disrupt the structure of the allergen and the cooked foods are usually well tolerated. There are indications that in many patients with OAS, symptoms worsen during the pollen season.
Oral allergy syndrome typically does not appear in younger children; the onset is more common in older children, teens, and young adults who have been eating the fruits and vegetables in question for years without any problems. Individuals with OAS typically have inhalant allergy to birch pollen, ragweed pollen, and grass pollens. Some studies have shown that treatment of inhalant allergies with allergy extract immunotherapy (allergy shots) can improve the symptoms of OAS.
The following is a list of pollens associated with OAS and related fruits, vegetables, and nuts:
Birch pollen (spring) – apple, almond, carrot, celery, cherry, hazelnut, kiwi, peach, pear, and plum
Grass pollen (late spring and summer) – celery, melons, oranges, peaches, tomato
Ragweed pollen (fall) – banana, cucumber, melons, sunflower seeds, zucchini
Cross-reactivity, but not oral allergy syndrome, can also occur between latex proteins allergens and foods such as bananas, avocados, kiwi, chestnut, and papaya. Latex allergic individuals can have serious generalized reactions to these fruits and vegetables.
If you or your child experiences a reaction beyond the mouth area after eating a fresh fruit or vegetable, that food could be considered a risk for anaphylaxis – a serious allergic reaction that is rapid, progressive, and can lead to life-threatening symptoms.
Consult with our board certified allergists for more information and to determine whether you should carry an epinephrine auto-injector to treat such potential severe reactions.
Written by Thomas B. Harper, III, MD.