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Patient education: Oral allergy syndrome (Beyond the Basics)

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Anna Nowak-Węgrzyn, MD
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Scott H Sicherer, MD, FAAAAI
Deputy Editor
Anna M Feldweg, MD
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WHAT IS ORAL ALLERGY SYNDROME?

Oral allergy syndrome (OAS), which is also called pollen-food allergy syndrome (PFAS or PFS), is a type of food allergy caused by uncooked fruits, raw vegetables, spices, and nuts. The most common symptom is itching of the mouth and throat, which begins quickly after a food is put in the mouth and usually lasts only a few minutes after the food is swallowed. OAS is seen in people who have allergies to pollens and is caused by allergens in fruits, vegetables, and nuts that are very similar to allergens in pollen.

This topic will focus on the cause, diagnosis, and treatment of OAS.

ORAL ALLERGY SYNDROME SYMPTOMS

The symptoms of OAS are:

Itching and tingling of the mouth, throat, and sometimes lips

Slight swelling and bumpiness of the mouth, throat, or lips

The symptoms of OAS usually begin a few minutes after you start eating the problematic food. Once you swallow the food, the symptoms usually go away within a few minutes. Most people stop eating the food because these symptoms are uncomfortable and unpleasant. Occasionally, the symptoms are so mild that people continue to eat the food, but this is less common.

Other symptoms that do not affect the mouth and throat are less common:

Some people develop itching, redness, or slight swelling of the hands if they peel or handle peeled raw fruits or vegetables that cause OAS, such as mangoes, apples, or white potatoes.

About 10 percent of people with OAS experience nausea or stomach upset. An even smaller number of people, probably fewer than 5 percent, develop more serious whole body allergic reactions, such as throat tightness, chest tightness, difficulty breathing, nausea, vomiting, diarrhea, or loss of consciousness [1]. (See 'When to seek help' below.)

There are some factors that can make an OAS reaction (or any type of allergic food reaction) more severe if present around the same time the food is eaten. The factors include eating a very large amount of the food, vigorous exercise after eating, drinking alcohol, being sick with a stomach virus or other minor illness, being very run down or sleep-deprived, or taking narcotics or other medicines for pain or fever (such as ibuprofen or aspirin). These factors may cause the food to be taken up by the body more rapidly or processed in a different way. If you notice that any of these factors make your reactions worse, avoid them in the future if you are going to be eating the foods that give you OAS symptoms.

Symptoms of OAS can vary depending upon the pollen season. Symptoms are usually most noticeable during the related pollen season and for a few months after. Also, OAS symptoms can be very specific to one variety of fruit. For example, Granny Smith apples tend to cause more OAS symptoms than Fuji apples.

WHO GETS ORAL ALLERGY SYNDROME?

Both children and adults can get OAS, but it is more common in adults. In fact, it is the most common type of food allergy in adults.

All people with OAS have pollen allergy. However, it is possible for a person to have bothersome OAS and have only a mild pollen allergy that he or she is unaware of. In such cases, skin and blood allergy tests reveal a pollen allergy. Allergy evaluation can clarify the diagnosis and establish an appropriate food avoidance and management plan.

Pollen allergy causes symptoms that occur at the same time each year:

Nose – Watery nasal discharge, blocked nasal passages, sneezing, nasal itching, mouth breathing, postnasal drip, pain and pressure in the face (see "Patient education: Allergic rhinitis (seasonal allergies) (Beyond the Basics)").

Eyes – Itchy, red eyes, feeling of grittiness in the eyes, swelling of the clear layer over the white of the eye, swelling of the skin around the eyes (see "Patient education: Allergic conjunctivitis (Beyond the Basics)").

Throat and ears – Sore throat, hoarse voice, congestion or popping of the ears, itching of the throat or ears.

Sleep – Frequent awakening, daytime fatigue, difficulty performing work or school tasks.

Pollen allergy is also called seasonal allergic rhinitis, seasonal allergies, or hay fever.

WHAT CAUSES ORAL ALLERGY SYNDROME?

OAS is caused by allergens in foods that come from plants. These are mainly uncooked fruits and raw vegetables. Some nuts can cause OAS symptoms, but since nuts can also trigger allergic reactions that are not related to pollen and can be severe, extreme caution is needed with nut reactions. Only foods that come from plants cause OAS. Other types of foods, such as dairy, seafood, or meats, do not cause OAS.

If you have OAS, you develop symptoms where these foods touch your mouth and throat. The allergens that cause OAS are easily destroyed by stomach acid, so the reaction usually stops as soon as the food is swallowed. Also for this reason, OAS rarely causes severe or life-threatening reactions. Cooking or heating also destroys the allergens, so cooked or canned fruits and vegetables rarely cause symptoms of OAS.

Some common examples of foods that cause OAS are listed in the table, along with the type of pollen that is related to these foods (table 1):

If you are allergic to birch tree pollen, you may develop oral symptoms when eating apples, peaches, apricots, cherries, plums, pears, almonds, hazelnuts, carrots, celery, parsley, caraway, fennel, coriander, aniseed, soybeans, or peanuts.

If you are allergic to ragweed pollen, you may develop oral symptoms when eating melons, zucchini, cucumber, kiwi, or bananas.

If you are allergic to grass pollen, you may develop oral symptoms when eating melons, tomatoes, oranges, swiss chard, or peanuts. You may also develop itchy, red hands when peeling raw white potatoes.

Although several foods are listed for each of the pollens above, most people with OAS react to just one or a small number of these foods.

HOW IS ORAL ALLERGY SYNDROME DIAGNOSED?

Your health care provider might be able to diagnose OAS simply by asking you some questions.

If your health care provider cannot tell if you have pollen allergy, he or she might refer you to an allergy specialist for more evaluation. The allergy specialist might recommend skin testing to pollens or to the foods that cause the symptoms [2] or the allergy specialist might ask you to eat the food while he or she observes your reaction. This is called a food challenge.

Skin testing and food challenges should be done by an allergy specialist, because these procedures must be done safely and interpreted correctly to be useful. Sometimes skin testing has to be done with fresh fruit and raw vegetables, because testing with commercial food extracts is not always accurate.

HOW IS ORAL ALLERGY SYNDROME TREATED?

In most cases, simply avoiding the foods that cause symptoms, in their raw forms, is sufficient treatment. This might involve avoiding dried or dehydrated forms of the foods, since dried foods are not usually cooked and can still cause symptoms. Sometimes, peeling a fruit (because much of the allergen is in the skin) or microwaving it for at least 10 seconds will destroy enough of the allergen that the fruit does not cause symptoms anymore, but this does not work for everyone or for all foods. As mentioned before, both raw and roasted nuts can cause OAS, and reactions to nuts should be treated with caution and discussed with a health care provider. There is no reason to avoid cooked, canned, or processed forms of the foods that do not cause symptoms.

Usually, OAS symptoms affecting the mouth and throat are mild, resolve quickly, and do not need treatment. However, more severe symptoms may occur rarely. If you have ever experienced allergic symptoms other than mild mouth or throat symptoms, such as chest tightness, difficulty breathing, nausea, severe throat discomfort (swelling, difficulty swallowing, drooling, hoarse voice), vomiting, diarrhea, or loss of consciousness, then you may need to carry an epinephrine autoinjector (Epi-Pen or similar device) for injecting epinephrine. Epinephrine is the best treatment for a severe allergic reaction [3]. Epinephrine autoinjectors are discussed in more detail elsewhere. (See "Patient education: Use of an epinephrine autoinjector (Beyond the Basics)" and "Patient education: Epinephrine autoinjectors (The Basics)".)

WHEN TO SEEK HELP

If you suspect that you have OAS, then you should discuss this with a health care provider. The most important reason for doing this is to make sure you do not have a more serious type of food allergy. This is especially important for reactions to nuts, as other forms of nut allergy can be very serious.

In addition, if you have ever experienced allergic symptoms from a raw fruit or vegetable or a nut that affected a part of the body other than the mouth or throat, you should be referred to an allergy specialist to determine if this is OAS or a more serious form of food allergy.

WHERE TO GET MORE INFORMATION?

Your health care provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our website (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Food allergy (The Basics)
Patient education: Allergy skin testing (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Food allergy treatment and avoidance (Beyond the Basics)
Patient education: Anaphylaxis symptoms and diagnosis (Beyond the Basics)
Patient education: Allergic rhinitis (seasonal allergies) (Beyond the Basics)
Patient education: Trigger avoidance in allergic rhinitis (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Clinical manifestations and diagnosis of oral allergy syndrome (pollen-food allergy syndrome)
Management and prognosis of oral allergy syndrome (pollen-food allergy syndrome)
Pathogenesis of oral allergy syndrome (pollen-food allergy syndrome)

The following organizations also provide reliable health information.

American Academy of Allergy, Asthma & Immunology (www.aaaai.org/conditions-and-treatments)

Food Allergy Research & Education (www.foodallergy.org/)

American College of Allergy, Asthma & Immunology (www.acaai.org/)

Asthma and Allergy Foundation of America (www.aafa.org/)

Literature review current through: Nov 2017. | This topic last updated: Mon Oct 30 00:00:00 GMT+00:00 2017.
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All topics are updated as new information becomes available. Our peer review process typically takes one to six weeks depending on the issue.