Food and Oral Allergy Syndrome (OAS) Causes,Symptoms and Treatment.

Author.

 Hayk S. Arakelyan. Full Professor in Medicine,

Doctor of Medical Sciences, Ph.D , Grand Ph.D .

Senior Expert of Interactive Clinical Pharmacology , Drug Safety,                                                                     Treatment Tactics, General Medicine and Clinical Research.                                                                                President of Rare and Incurable Diseases Association.

Yerevan-Armenia, Tokyo-Japan.

“Natural forces within us are

 the true healers of disease.”

“ Hippocrates”

Introduction.

Oral allergy syndrome (OAS) is a type of food allergy classified by a cluster of allergic reactions in the mouth and throat in response to eating certain (usually fresh) fruits, nuts, and vegetables that typically develops in adults with hay fever. OAS is not a separate food allergy, but rather represents cross-reactivity between distant remnants of tree or weed pollen still found in certain fruits and vegetables. Therefore, OAS is only seen in people with seasonal pollen allergies, and mostly people who are allergic to tree pollen. It is usually limited to ingestion of uncooked fruits or vegetables. Another term used for this syndrome is pollen-food allergy. In adults up to 60% of all food allergic reactions are due to cross-reactions between foods and inhalative allergens.

OAS is a Type 1 or IgE-mediated hypersensitivity, which is sometimes called a "true allergy". The body's immune system produces IgE antibodies against pollen; in OAS, these antibodies also bind to (or cross-react with) other structurally similar proteins found in botanically related plants.

OAS can occur any time of the year but is most prevalent during the pollen season. Individuals with OAS usually develop symptoms within minutes of eating the food. If you suffer from hay fever (allergic rhinitis) caused by pollen, your mouth or throat may become itchy after eating an apple or celery. This happens in up to 50 to 75% of adults allergic to birch tree pollen. This reaction occurs because the proteins found in some fruits and vegetables are very similar to those found in pollen. These proteins can confuse the immune system and cause an allergic reaction or make existing symptoms worse, which is referred to as cross-reactivity. In the case of pollen and foods, the result of cross-reactivity is called oral allergy syndrome (OAS) also known as pollen fruit syndrome (PFS).OAS is a form of a contact allergic reaction that occurs upon contact of the mouth and throat with raw fruits or vegetables. The most frequent symptoms of OAS include itchiness or swelling of the mouth, face, lip, tongue and throat. Symptoms usually appear immediately after eating raw fruits or vegetables, although in rare cases, the reaction can occur more than an hour later. OAS is generally considered to be a mild form of food allergy. Rarely, OAS can cause severe throat swelling leading to difficulty swallowing or breathing. In a person who is highly allergic, a systemic reaction, called anaphylaxis (an-a-fi-LAK-sis), may be caused by a pollen cross-reactive raw fruit or vegetable, but this is very uncommon. OAS can occur at any time of the year.

Causes and Diagnosis of  Oral Allergy Syndrome.

OAS produces symptoms when an affected person eats certain fruits, vegetables, and nuts. Some individuals may only show allergy to one particular food, and others may show an allergic response to many foods.

Individuals with an allergy to tree pollen may develop OAS to a variety of foods. While the tree pollen allergy has been worked out, the grass pollen is not well understood. Furthermore, some individuals have severe reactions to certain fruits and vegetables that do not fall into any particular allergy category. When tropical foods initiate OAS, allergy to latex may be the underlying cause.

Because the allergenic proteins associated with OAS are usually destroyed by cooking, most reactions are caused by eating raw foods. The main exceptions to this are celery and nuts, which may cause reactions even after being cooked.

Cross reactions.

Allergies to a specific pollen are usually associated with OAS reactions to other certain foods. For instance, an allergy to ragweed is associated with OAS reactions to banana, watermelon, cantaloupe, honeydew, zucchini, and cucumber. This does not mean that all sufferers of an allergy to ragweed will experience adverse effects from all or even any of these foods. Reactions may be associated with one type of food, with new reactions to other foods developing later. However, reaction to one or more foods in any given category does not necessarily mean a person is allergic to all foods in that group.

Alder pollen: almonds, apples, celery, cherries, hazel nuts, peaches, pears, parsley, raspberry, strawberry.

Birch pollen: almonds, apples, apricots, avocados, bananas, carrots, celery, cherries, chicory, coriander, fennel, fig, hazel. nuts, kiwifruit, nectarines, parsley, parsnips, peaches, pears, peppers, plums, potatoes, prunes, soy, strawberries, wheat, jackfruit; Potential: walnuts.

Grass pollen: fig, melons, tomatoes, oranges, celery, peach.

Mugwort pollen : carrots, celery, coriander, fennel, parsley, peppers, sunflower, mustard.

Ragweed pollen : banana, cantaloupe, cucumber, green pepper, paprika, sunflower. seeds/oil, honeydew, watermelon, zucchini, echinacea, artichoke, dandelions, honey (if bees pollinate with pollen from wild flowers), hibiscus or chamomile tea.

Possible cross-reactions (to any of the above): berries (blueberries, raspberries, etc.), citrus (oranges, lemons, etc.), grapes, mango, figs, peanut, pineapple, pomegranates, watermelon, atemoya, cherimoya, sugar-apple, custard apple, soursop.

Diagnosis of  Oral Allergy Syndrome.

The patient typically already has a history of atopy and an atopic family history. Eczema, otolaryngeal symptoms of hay fever or asthma will often dominate leading to the food allergy being unsuspected. Often well-cooked, canned, pasteurized, or frozen food offenders cause little to no reaction due to denaturation of the cross-reacting proteins, causing delay and confusion in diagnosis as the symptoms are elicited only to the raw or fully ripened fresh foods. Correct diagnosis of the allergen types involved is critical. OAS sufferers may be allergic to more than just pollen. Oral reactions to food are often mistakenly self-diagnosed by patients as caused by pesticides or other contaminants. Other reactions to food—such as lactose intolerance and intolerances which result from a patient being unable to metabolize naturally occurring chemicals (e.g., salicylates and proteins) in food—need to be distinguished from the systemic symptoms of OAS.

Testing.

Many people are unaware that they have OAS. However, if swelling, tingling or pain develops while eating certain foods, then it is wise to see an allergy specialist. Before a diagnosis can be made, keep a food diary. This is important as the physician can then perform an allergy test. Before testing is started, a comprehensive history is obtained so that random testing is avoided. The diagnosis of OAS may involve skin prick tests, blood tests, patch tests or oral challenges. When OAS is suspected, the oral challenge test is ideal.

Exams.

To confirm OAS, the suspected food is consumed in a normal way. The period of observation after ingestion and symptoms are recorded. If other factors such as combined foods are required, this is also replicated in the test. For example, if the individual always develops symptoms after eating followed by exercise, then this is replicated in the laboratory.

Signs and Symptoms of  Oral Allergy Syndrome.

OAS sufferers may have any of a number of allergic reactions that usually occur very rapidly, within minutes of eating a trigger food. The most common reaction is an itching or burning sensation in the lips, mouth, ear canal, or pharynx. Sometimes other reactions can be triggered in the eyes, nose, and skin. Swelling of the lips, tongue, and uvula, and a sensation of tightness in the throat may be observed. If a sufferer swallows the food, and the allergen is not destroyed by the stomach acids, it is likely that there will be a reaction from histamine release later in the gastrointestinal tract. Vomiting, diarrhea, severe indigestion, or cramps may occur. Rarely, OAS may be severe and present as wheezing, vomiting, hives, low blood pressure, or anaphylaxis.

Treatment of  Oral Allergy Syndrome.

OAS must be managed in conjunction with the patient's other allergies, primarily the allergy to pollen. The symptom severity may wax and wane with the pollen levels. Published pollen counts and seasonal charts are useful but may be ineffective in cases of high wind or unusual weather, as pollen can travel hundreds of kilometers from other areas. In addition, patients are advised to avoid the triggering foods, particularly nuts. Peeling or cooking the foods has been shown to eliminate the effects of some allergens such as mal d 1 (apple), but not others such as celery or strawberry. In the case of foods such as hazelnut, which have more than one allergen, cooking may eliminate one allergen but not the other.

Antihistamines may also relieve the symptoms of the allergy by blocking the immune pathway. Persons with a history of severe anaphylactic reaction may carry an injectable emergency dose of epinephrine (such as an EpiPen). Oral steroids may also be helpful. Allergy immunotherapy has been reported to improve or cure OAS in some patients. Immunotherapy with extracts containing birch pollen may benefit OAS sufferers of apple or hazelnut related to birch pollen-allergens. Even so, the increase in the amount of apple/hazelnut tolerated was small (from 12.6 to 32.6 g apple), and as a result, a patient's management of OAS would be limited.

If you have any questions concerning “ Food and Oral Allergy Syndrome (OAS) Causes,Symptoms and Treatment”, interactive clinical pharmacology , or any other questions, please inform me . 

      Prof. Hayk S. Arakelyan