Oral Allergy Syndrome: Practical Tips for when Pollen and Food Connect

If you suffer from pollen allergies and hay fever, you might also find that some foods cause you problems too. If you get an itchy mouth or throat from eating certain fruits and vegetables, it could be oral allergy syndrome (OAS). This phenomenon is also known as pollen food allergy syndrome (PFAS). Find out more about the links between different types of grass and tree pollen allergies and specific foods and tips for managing symptoms.

Fresh fruit and vegetables with text "oral allergy syndrome, practical tips for when pollen and food connect"

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What is oral allergy syndrome?

Oral allergy syndrome is the name given to generally mild reactions to eating some raw fruits, vegetables, nuts or seeds. It is also known as pollen food allergy syndrome, because it affects people who have pollen allergies to certain types of tree or grass pollens. This means that people with hay fever (allergic rhinitis) might be affected by OAS/PFAS. The proteins in these pollens are similar to the proteins in some foods, causing the immune system to react.

It is more common for older children, teens and adults with hay fever to develop oral allergy syndrome.

Symptoms of oral allergy syndrome

The most common symptoms of oral allergy syndrome are itchiness or tingling of the lips, mouth, tongue or throat. Some people may get swollen lips or hives around the mouth. The symptoms are usually limited to the mouth and go away once the food is removed, so no treatment is required.

OAS is a form of contact reaction. Some people also experience itchy hands when cutting up raw fruit and vegetables like potatoes and tomatoes.

Oral allergy syndrome might be diagnosed on symptoms alone, or sometimes an allergist will do skin testing with the offending foods.

Is it oral allergy syndrome or a more serious food allergy?

If you find that you are experiencing allergy type symptoms from any food, you should speak to your doctor and ask for a referral to an allergist/immunologist. This is especially the case if you find that you are experiencing symptoms like itchy mouth, throat and hives from nuts, as nuts are one of the top food allergens. Kiwi fruit can also cause serious allergic reactions. An allergist will be able to help you determine whether you have a food allergy or are experiencing pollen food allergy syndrome symptoms.

If your symptoms are more than just an itchy or tingly mouth, you may have a food allergy. For serious symptoms such as widespread skin reactions (hives and itching on the body), low blood pressure, airway symptoms (swollen tongue or throat, wheezing or trouble breathing), nausea, vomiting or diarrhoea or fainting/collapse, seek urgent medical attention. These are symptoms of a severe reaction (anaphylaxis).

Cross-reactivity of different pollens and foods

There are may different types of pollens that can cause hay fever (allergic rhinitis) symptoms. And different types of common allergy-causing pollens can cross-react with different foods. Here are some of the most common allergenic tree and grass pollens and examples of the foods that they are related to.

Birch tree pollen

Birch pollen allergy is very common in Europe, but is also a problem in other parts of the world (including here in Australia). Pollen from birch trees is highly allergenic and unfortunately can cross-react with a wide range of fruits, vegetables, legumes and nuts. It is one of the main causes of OAS/PFAS.

Birch tree seeds and list of foods that may cause oral allergy symptoms if allergic to birch pollen

Alder pollen

Related to birch trees, alder trees are also a common cause of hay fever. They are native to Europe and the UK, but pollen from alder trees is a problem in the United States, Australia and many other countries where alder trees are now prevalent. Alder tree flowers are produced on hanging ‘catkins’, which release a large amount of allergenic pollen in spring.

Alder tree catkins with list of foods associated with oral allergy syndrome from alder tree pollen

Ragweed pollen

Pollen from ragweed is another major cause of hay fever and is also associated with oral allergy syndrome. Ragweed produces very large amounts of pollen, which is very light and can travel a long way. It is native to North America but is now found around the world, thriving in temperate climates. If you are allergic to ragweed pollen, you may experience oral allergy syndrome symptoms from eating bananas, melons, zucchini and cucumber amongst other fresh foods.

Ragweed plant with list of related foods that can cause oral allergy syndrome

Mugwort pollen

Mugwort (also known as wild wormwood or felon herb, and common wormwood.) is a useful herb. But it is also now a widespread weed in many countries including Australia, Europe and northern parts of Asia. It’s a common cause of hay fever in Europe especially.

If you are allergic to mugwort pollen, you might experience oral allergy syndrome symptoms from eating certain types of vegetables and herbs.

Mugwort weed and list of foods that may cause oral allergy symptoms if allergic to mugwort pollen

Timothy grass pollen

Another highly allergenic grass is timothy grass, a native perennial grass from Europe and northern Asia. It is grown in temperature climates around the world as a pasture hay and fodder. Timothy grass produces large amounts of pollen in early summer. People who are allergic to timothy grass pollen can experience oral allergy syndrome when eating citrus fruits, peaches, tomatoes and melons and may react to raw potato too.

Timothy grass stems and list of foods that may cause oral allergy symptoms if allergic to timothy grass pollen

Ryegrass pollen

Ryegrass is native to Europe but is now found all over the world. It is a major airborne allergen in Australia and the United States (in more moderate climates). This weed grows anywhere that grass grows, not just in rural areas. You can find it in backyards and playgrounds and even on the side of the road.

People with ryegrass allergies might experience oral allergy syndrome from eating fruit like bananas, pineapple and melons, tomato, zucchini, peanuts or hazelnuts.

Ryegrass releasing pollen and list of foods that may cause oral allergy symptoms if allergic to ryegrass pollen

How to minimise OAS symptoms

If you suffer from an itchy or tingling mouth after eating certain fruits, vegetables, seeds or nuts, the easiest way to fix it is to avoid the food in question.

However, there are some ways that you may be able to still enjoy them:

  • Some people can tolerate the foods by removing the skin first, as more of the protein causing the reactions is under the skin and is removed by peeling. Cooking the food first may also help, because heat changes the proteins so they are less likely to cause reactions. For example, you might have symptoms from eating a raw apricot, but be able to eat tinned apricots or apricots cooked in a pie.
  • If you get itchy hands from cutting up raw fruit or vegetables, gloves can help.
  • Symptoms might be worse during the pollen season but only mild at other times of the year. So you may choose to avoid the offending fruit only during times when you have hay fever symptoms due to grass or tree pollen.

If you have hay fever and oral allergy syndrome, talk to an allergist about whether you might benefit from desensitisation (immunotherapy or “allergy shots“).

Does oral allergy syndrome affect everyone with pollen allergies?

Not everyone with pollen allergies will suffer from oral allergy syndrome. I personally am highly allergic to both birch trees and a range of grasses including timothy grass. In fact, I am currently having allergy shots for 6 different types of grass and tree pollens to manage my severe hay fever symptoms. However I have never noticed any symptoms from eating the common cross-reactive food culprits. Another family member on the other hand also has severe pollen allergies and definitely gets an itchy mouth from melons, especially cantaloupe (rockmelon) and honeydew melons, and kiwi fruit.

If you have pollen allergies but don’t experience any symptoms of oral allergy syndrome, there’s no reason to avoid the related foods.

References and more information

If you think you may have oral allergy syndrome, talk to your doctor about a referral to an allergist to discuss your symptoms and how best to treat them.

For more information about oral allergy syndrome/pollen allergy syndrome, see the following resources from allergy organisations that we’ve referred to in this post:

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