Food Allergies In Adults: Oral Allergy Syndrome

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In some individuals, eating a particular food or foods can trigger a response from the immune system. Some food allergies appear in infancy while other types of food allergies manifest later in childhood or adulthood. When a certain substance is consumed, the body perceives the substance as a threat and responds by triggering an allergic reaction. For many people who are allergic to particular fruits and vegetables, they developed the allergy later in childhood or as an adult. 

How Oral Allergies Develop

People with hay fever are allergic to certain kinds of pollen and develop symptoms of running nose, itchy throat, and watery eyes when exposed to triggering pollen. Over time, the pollen allergy can also cause an allergic reaction when certain raw fruits or vegetables are consumed. This type of food allergy is called oral allergy syndrome.  Approximately one-half to three-fourths of people with a birch pollen allergy develop oral allergy syndrome. Other common pollen that causes oral allergy syndrome includes ragweed, mugwort, and grasses such as timothy. A skin prick test can be used to test for pollen allergies in patients who experience oral allergy symptoms when eating fruits or vegetables that trigger a reaction. 

Cross Reactivity

Pollen that causes a food allergy is called "cross reactive" because the proteins present in pollen that trigger hay fever are also present in some types of fruits and vegetables. The triggering proteins cause the body to release histamines, which are responsible for the symptoms of an allergic reaction. People allergic to birch may develop oral allergies to orchard fruits such as apples, pears, peaches, cherries, and plums. A ragweed allergy can cause OAS symptoms when eating melons or cucumbers, and mugwort can cause an allergy to broccoli, cabbage, and cauliflower. People allergic to oranges and tomatoes are also allergic to pollen from grasses.  


Oral allergy symptoms generally occur only in and around the mouth and throat, unlike other food allergies that can cause a reaction in other areas of the body. When a person with OAS eats certain types of raw fruits or vegetables, the immune system releases histamines that cause itching or tingling in the lips, tongue, hard or soft palate, and throat. Swelling of these tissues is less common but can become dangerous if there is excessive swelling in the throat that makes it difficult to breathe or swallow. Once the food is swallowed, the allergic reaction subsides. 

Management and Prevention

Avoiding raw produce that is cross reactive with a pollen allergy is an effective way to prevent symptoms from occurring. People with OAS typically experience an allergic reaction when they eat triggering fruits and vegetables raw. Some kinds of cooked fruits and vegetables are less likely to cause an immune response. For example, cooking reduces the allergens in apples but is not effective for reducing the allergens in celery or strawberries. Some fruits contain a greater concentration of histamine-inducing proteins in the skin. Removing the peel from thin-skinned fruits can reduce the severity of the reaction and symptoms.

Treating OAS

While avoidance can prevent symptoms from occurring, there is no treatment for the actual cause of the allergy itself. However, the itching and tingling sensations, as well as any swelling that occurs when eating fruits and vegetables, can be treated by taking an antihistamine. In mild cases, even rinsing the mouth with water can help relieve symptoms. In rare cases of a severe reaction that causes enough swelling to interfere with breathing or swallowing, your ENT specialist may prescribe an epinephrine injector to keep on hand in case you accidentally consume an allergenic food.

For more information, you can contact clinics like Mid America Ear, Nose, & Throat Clinic PC.