What is Oral Allergy Syndrome?

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  • Written By: D. Jeffress
  • Edited By: Jenn Walker
  • Last Modified Date: 31 October 2018
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Oral allergy syndrome is a condition in which a person experiences an allergic reaction to certain foods, most commonly fresh vegetables, fruits, and nuts. Unlike other food allergies, oral allergy syndrome is not triggered by the foods themselves. Rather, the allergic response occurs because the body's immune system mistakes food proteins for pollen spores that have similar chemical and physical properties. An individual who is allergic to pollen, then, can experience a reaction when eating foods that have homologous proteins. A person who experiences allergic reactions to food or other pathogens should be evaluated by a medical professional to receive a diagnosis and learn about treatment options.

Pathologists have identified several connections between pollens and foods based on the proteins they contain. An individual who has an allergic reaction to ragweed, for example, may experience a similar reaction after eating bananas, melons, or cucumbers. Allergies to other trees and grasses can cause symptoms when eating tomatoes, cherries, carrots, hazelnuts, or many other common foods.


When a person with oral allergy syndrome eats a food associated with a pollen, his or her immune system recognizes the normally harmless proteins as potential threats. The immune system releases chemicals called histamines to combat the proteins, which causes the mouth, throat, and sinuses to become inflamed and produce mucus. As a result, the person's lips, gums, and tongue swell and his or her eyes become watery and itchy. In the case of a severe reaction, throat swelling can restrict the airways enough to make breathing very difficult.

Most mild cases of oral allergy syndrome can be treated at home with over-the-counter oral antihistamines. If an individual knows which food triggered his or her symptoms, the offensive product should be avoided in the future. Immediate medical care should be sought in the event of a severe reaction that restricts breathing. A doctor can inject a solution of epinephrine or a similar drug to immediately stop the immune system's release of histamines.

Following immediate treatment, a patient is usually tested for specific allergens. A specialist can conduct a series of blood or skin-prick tests to determine which pollens and corresponding foods trigger an immune system response. After identifying the causes of oral allergy syndrome, the doctor may decide to prescribe an allergy medication or arrange for the patient to receive regular allergy shots to help manage symptoms. By following the doctor's recommendations and staying away from known triggers, a person with oral allergy syndrome can usually avoid future problems.



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