Birch Tree Pollen and Oral Allergy Syndrome

By: Alletess Medical Laboratory

They thrive mostly in the Northern Hemisphere, they grow quickly and are commonly known for having white or multicolored bark, and they tend to trigger pollen allergies in individuals. 

What kind of tree are we talking about?


If you deal with pollen allergies between January-April, it could be due to wind pollinated birch pollen. Pollen counts can shift greatly each year, with symptoms ranging from a runny nose and sneezing, to something called oral allergy syndrome (OAS), which is caused by a high level of cross reactivity. 

But first, let’s take a step back… 

Cross reactivity and Oral Allergy Syndrome, what does it all mean?  

Similarities in protein structures confuse the immune system into thinking it is one thing, when it is not. Take, for example, birch tree pollen and apples. These two substances seem quite different, right? 

Well… At the biological level of protein structures, birch tree pollen and apples actually have many similarities, and oftentimes are identified by the immune system as being similar. This is called cross reactivity, and cross reactivity can cause the immune system to respond as experiencing allergy symptoms

So, what does this mean in the case of birch tree pollen? 

If you are a person who has an allergic reaction to birch tree pollen, this may also trigger your immune system to respond as an allergic reaction when eating an apple (or other foods that have similar protein structures). Although we are talking about the high levels of cross reactivity between birch tree pollen and apples, there are many other allergens that cross react with one another, making the diagnosis of the true allergen a bit difficult. 

Let’s take a look at this example to better understand this phenomenon. 

Imagine you are someone who is allergic to birch tree pollen. You try to stay away from these trees, but sometimes it is inevitable that you come in contact with this pollen, and this triggers a response that includes sneezing, a runny nose, and an itchy throat. Hours later, after the symptoms reside, this individual then eats a piece of fruit. This fruit causes the individual to experience the same symptoms that they just went through with pollen, but they of course do not think these symptoms correlate! Now, this individual believes that they are allergic to this fruit they just ingested, since they are experiencing allergy symptoms. This individual does not know that what they are experiencing is called Oral Allergy Syndrome, which is the result of cross reactivity between pollen and specific foods. 

If you are someone who has an allergic reaction to pollen, and also has an allergic reaction when eating specific foods (vegetables, fruits, nuts, or wheat), this cross reactivity is called Oral Allergy Syndrome (OAS). Of adults who are allergic to pollen, about 60% of them will experience OAS, and about 25% of children with allergic rhinitis (hay fever) will also have OAS. 

Common Symptoms of OAS

Similar to other allergies, symptoms of OAS include tingling or itching mouth, trouble swallowing, swollen mouth, tongue, or throat, and more. These symptoms are immediate but may last up to several hours, and the severity of symptoms can depend on the pollen count level during that time of year. Although anaphylaxis is rare, it is possible that an allergic reaction could become more systemic. 

What foods can trigger an allergic response? 

Foods are most likely to trigger a response in their raw form, so foods should be cooked if possible. Although not everyone with a birch tree allergy will also have an allergic reaction when eating certain foods, these foods have a high chance of causing a reaction. 

Fruits and Vegetables: 

  • Apple, Pear, Apricot, Fig, Avocado, Strawberry, Mango, Dried Plum, Banana, Peach, Cherry, Nectarine, Plum, Kiwi 
  • Carrot, tomato, fennel, cumin, cilantro, parsnip, dill, potato, celery

Nuts and Grains:

  • Peanut, Walnut, Hazelnut, Almond
  • Beans, Soy, Peas, Wheat, Lentils 

**please ask your provider for a full list 

What to do if you suspect OAS?

Although there is no specific test that confirms an individual has OAS, if you are experiencing similar symptoms, discuss possible options with your doctor. Due to Oral Allergy Syndrome being the result of cross reactivities, your doctor may order you an allergen component test, which tests for specific proteins within an allergen. Your doctor may order you this type of test because it may help determine what pollens and foods may trigger an allergic reaction due to cross reactivities. The results of this test will be able to help your provider determine an optimal treatment plan for you, as well.