October 3, 2018

What Should You Know About Oral Allergy Syndrome?

Sneezing, runny nose, red and itchy eyes and other symptoms of hay fever affect a third of people living in North America. What is more, about a third of hay fever sufferers also experience a condition called oral allergy syndrome.


Oral allergy syndrome, also known as OAS, is a form of food allergy that affects the area of the mouth, throat and lips and causes tingling and itching. OAS is directly related to pollen allergies, which means that allergic proteins causing the reaction are similar to those in pollen of hay fever-causing plants. The symptoms can be triggered by various fruits, vegetables, seeds, nuts, or spices.

Usually, oral allergy syndrome is not a life-threatening condition, though it can be quite irritating. In fact, OAS is more common other many other food allergies, including allergies to milk, eggs, peanuts, and fish.

People allergic to birch and alder pollen are at a higher risk of developing oral allergy syndrome. Depending on the geographical location, OAS affects from 20 to 70 percent of people with birch and alder allergies.

In general, oral allergy syndrome is quite common in North America. However, experts don’t think that it is increasing.

Why Do Hay Fever Sufferers React to Certain Foods?


People allergic to tree pollen often develop oral allergies after eating certain plant-based foods. This happens because the allergenic proteins found in pollen are also present in various foods.

Proteins coming from different may be so similar that the immune system not be able to differentiate between them. For example, birch pollen and apple peel contain similar allergens.

In birch tree pollen, a protein called Bet v 1 is the most common allergen. It is very similar to a protein called Aln g 1, which is found in alder. These proteins, also known as pan-allergens, protect the fruit or vegetables from infection, as well as during stress.

Bet v 1 is also found in various plants, even those that are not related. Thus, it is present in apples, kiwis, plums, carrots, potatoes, celery, almonds, hazelnuts, sunflower seeds, as well as spices like basil, oregano and dill.

If you have a birch pollen allergy, your immune system reacts and releases specific antibodies every time it is exposed to the allergen. Therefore, if you eat a food that contains protein similar to Bet v 1, your body will produce these antibodies too.

In addition, people with grass pollen allergies may also react to foods like kiwi, melons, oranges, tomatoes, peanuts, and others, while those suffering from ragweed allergy may develop the OAS symptoms after eating banana, melons, cucumber or zucchini.

Besides, in case of a ragweed allergy, it is also possible to experience cross-reactions to honey, chamomile and echinacea. However, this is not caused by oral allergy syndrome. Instead, cross-reactivity occurs because they come from the same botanical family.

Why Do Apples Cause Oral Allergy?


Trees like oak, maple and poplar also produce allergy-inducing pollen. But unlike birch or alder pollen, their pollen doesn’t share allergenic proteins with plant-based foods.

However, even if you are allergic to birch, alder, grass or ragweed, this doesn’t necessarily mean that you will experience oral allergy syndrome after eating the foods mentioned above. Besides, if you do have OAS, the reaction is not necessarily triggered by every food on the list.

There are fruits and vegetables that are more likely to trigger oral allergy syndrome than others. For example, you are at a higher risk of having irritation if you eat apples than if you eat pears. When it comes to the plum family, cherries and peaches were found to be more likely to cause a reaction, compared to apricots and plums.

What is more, the variety of the fruit you are eating can also influence the likelihood of a reaction. Thus, according to some studies conducted in Europe, gala and golden delicious apples contain more allergic proteins and therefore, are more likely to trigger a reaction, than Braeburn or Santana apples.

Is Oral Allergy Syndrome Also Seasonal?


Depending on the factors like genetics and geographical location, people tend to react to specific foods.

Although oral allergy syndrome develops in people with hay fever, which is seasonal and lasts for several weeks or months, those with OAS may experience the symptoms year-round. Sometimes, the symptoms may get worse during pollen allergy season.

The good news is that most of the pan-allergens are neutralized when cooked, meaning you can eat cooked foods without having a reaction.

Is It Safe to Eat the OAS-Causing Foods Cooked?


Some people can react to raw fruits or vegetables but eat them in a cooked form without any problem. In this case, they may think that the reaction is triggered by pollen that sticks to the fruit surface, or pesticides sprayed on it, or wax. In fact, it’s oral allergy syndrome.

Cooking (boiling, baking or microwaving) can change the three-dimensional structure of the allergenic proteins in most foods except celery and nuts. As a result, the oral allergy offender is not likely to attract the pollen-allergen antibodies.

Can Oral Allergy Lead to Anaphylaxis?


Oral allergy syndrome usually causes relatively mild symptoms, even when triggered by common food allergens like tree nuts or peanut. However, severe reactions, such as anaphylaxis, may occur in 1 to 2 percent of people affected by OAS.

Research suggests that in case of oral allergy, anaphylaxis is more likely to be triggered by tree nuts (especially hazelnuts), kiwi, apples, peaches, celery, and apricots. This doesn’t mean, however, that eating these foods will always lead to life-threatening symptoms.

In addition, the risk of severe OAS reaction will be higher, if a person consumes a large dose of the offending food quickly, drinks alcohol or does exercise.

When it comes to anaphylaxis, it may be difficult to determine whether it’s caused by a cross-reaction to pollen allergen or triggered by the food itself.

It is also possible that a person with a birch pollen allergy has positive allergy test results to apples, peanuts, carrots, and other foods but doesn’t actually react to these foods. These false-positive tests can make it difficult for allergist to make an accurate diagnosis. Fortunately, there are new protein “component” tests available that can help to determine the exact allergy trigger.

Share this: