Oral Allergy Syndrome

Have you ever taken a bite out of an apple or nibbled a carrot only to feel a tingling and itching sensation in your mouth? If so then it is possible you have oral allergy syndrome (OAS), an often mild allergic reaction to eating certain raw fruit, vegetables and nuts. Also known as pollen food syndrome (PFS) this allergy usually occurs in people who suffer from hayfever and is a cross reaction with proteins in the food that are similar to those found in pollen.

The condition is actually quite common although many people affected by it have never even heard of OAS or PFS. Whilst you do not actually have to suffer from any of the usual hayfever symptoms to have OAS, you do need to test positive to pollen. The type of pollen you are allergic to will affect the range of fruits, vegetables or nuts you react to. In the U.S. and UK birch tree pollen is the most common type involved in these cross reactions with around 50 to 75% of who are allergic to the pollen also showing OAS symptoms. In general around 40% of hay-fever sufferers will experience some degree of pollen-food allergy syndrome.

Oral allergy syndrome usually develops in early adulthood and unlike some other food allergies, the symptoms remains mild. However, in rare cases reactions can become severe with the potential of anaphylaxis. It is also important not to assume that a reaction to nuts is caused by OAS and not a nut allergy which poses a much greater risk of a future severe allergic reaction.

Oral Allergy Syndrome symptoms

As the name suggests most of the symptoms of oral allergy syndrome are confined to the mouth.  These symptoms will occur within a matter of minutes of placing the raw vegetable, fruit or nut in the mouth. They are generally short-lived and do not persist for long or cause further irritation after the food is swallowed.

• Itching and tingling of the mouth, lips, and throat
• Swelling of tongue or lips
• Scratchy / itchy throat
• Itchy ears are occasionally reported

In very rare cases symptoms may present elsewhere on the body as part of a system-wide reaction. This may include a hives, vomiting or wheezing / breathing difficulties. Any reaction beyond the mouth should be taken seriously as it is an indicator of a risk of anaphylaxis.

Generally the symptoms and severity of the reaction remains consistent with OAS. However, they may become slightly worse during the pollen season.

Avoid raw food

Whilst we are often told of the healthy virtues of raw fruit and vegetables, if you have oral allergy syndrome it can often be better to cook them. This is because heating up the food causes the allergen proteins inside them to denature, or break down. The same may be true of processed foods; in canned, pasteurized or even frozen foods the protein may be deactivated. This is less likely to be the case in dried foods.

Another potential way to neutralize the allergy-causing proteins in fruits and vegetables is to peel them. This is because the allergy causing proteins are often concentrated in the skin.

Pollen-Food allergy cross-reactivity

Reactions to fruits and vegetables can be quite specific and much of this depends on the type of pollen the person is allergic to. On the other hand some sufferers of OAS are allergic to a wide range of different fruit and vegetables. This is largely controlled by the degree of sensitivity to the particular allergen protein in the pollen and how similar it is to the protein found in the food. The main allergen in birch pollen is Bet v 1 and this is similar to a large number of proteins found in plant foods.

So, the seasonal allergy you have will to a large extent determine which foods you may experience an allergic reaction to. The table at the bottom of the page outlines some of the main pollen allergies and the foods they are likely to cross-react with. Please note though, it is possible to be allergic to just one or all the foods associated with a particular type of pollen. So you might be allergic to mugwort pollen and be allergic to broccoli but not any of the spices.

As well as there being a potential for cross reactivity between pollens and foods there may also be a link between latex allergy and certain foods. These include; avocados, bananas, chestnuts, kiwi fruit and papaya.

Fruit, vegetable and nuts cross reactivity with pollen

• Tomatoes and cucumbers are technically fruits but more often included with vegetables.