Oral allergy syndrome (OAS) or pollen-food allergy is a type of

food allergy A food allergy is an abnormal immune response to food. The symptoms of the allergic reaction may range from mild to severe. They may include itchiness, swelling of the tongue, vomiting, diarrhea, hives, trouble breathing, or low blood pressur ...

classified by a cluster of allergic reactions in the mouth and throat in response to eating certain (usually fresh)

fruits In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in partic ...

, nuts, and

vegetables Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still commonly used and is applied to plants collectively to refer to all edible plant matter, including the flowers, fruits, stems ...

that typically develops in adults with

hay fever Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, i ...

. 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 Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametop ...

. It is usually limited to ingestion of uncooked fruits or vegetables. 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

immunoglobulin E Immunoglobulin E (IgE) is a type of antibody (or immunoglobulin (Ig) " isotype") that has been found only in mammals. IgE is synthesised by plasma cells. Monomers of IgE consist of two heavy chains (ε chain) and two light chains, with the � ...

-mediated

hypersensitivity Hypersensitivity (also called hypersensitivity reaction or intolerance) refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity. They are usually referred to as an over-reaction of the immune ...

, which is sometimes called a " true allergy". The body's immune system produces IgE

antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of ...

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.

Signs and symptoms

Individuals with OAS 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 The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...

. Sometimes other reactions can be triggered in the eyes, nose, and skin. Swelling of the lips, tongue, and

uvula The palatine uvula, usually referred to as simply the uvula, is a conic projection from the back edge of the middle of the soft palate, composed of connective tissue containing a number of racemose glands, and some muscular fibers. It also conta ...

, and a sensation of tightness in the throat may be observed. Once the allergen reaches the stomach, it is broken down by the acid, and the allergic reaction does not progress further.{{rp, 405} The natural course of the disease is that it usually persists.{{rp, 407 If an affected person swallows the raw 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 The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...

Vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenter ...

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...

, severe

indigestion Indigestion, also known as dyspepsia or upset stomach, is a condition of impaired digestion. Symptoms may include upper abdominal fullness, heartburn, nausea, belching, or upper abdominal pain. People may also experience feeling full earlier t ...

, or

cramps A cramp is a sudden, involuntary, painful skeletal muscle contraction or overshortening associated with electrical activity; while generally temporary and non-damaging, they can cause significant pain and a paralysis-like immobility of the aff ...

may occur.{{cite journal , last=Pong , first=Anthony Ham , title=Oral Allergy Syndrome , date=June 2000 , journal=Allergy/Asthma Information Association (AAIA) Newsletter Rarely, OAS may be severe and present as wheezing, vomiting, hives,

low blood pressure Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the systolic blood pressure (the top number) and the di ...

,{{Cite web , title=Oral Allergy Syndrome , url=http://www.oralallergy.net/ , url-status=dead , archive-url=https://web.archive.org/web/20121005084931/http://www.oralallergy.net/ , archive-date=2012-10-05 , access-date=2010-01-26 , website=oralallergy.net or

anaphylaxis Anaphylaxis is a serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of use of emergency medication on site. It typically causes more than one of the follo ...

.{{cite web , last=More , first=D. , title=Oral Allergy Syndrome , url=http://allergies.about.com/od/foodallergies/a/oas.htm , date=April 28, 2007 , publisher=About.com , access-date=2008-01-25

Development, causes

A person with an allergic disposition is sensitized to allergenic pollen proteins through the respiratory route can develop an allergy to heat labile food proteins (for example

profilin Profilin is an actin-binding protein involved in the dynamic turnover and reconstruction of the actin cytoskeleton. It is found in all eukaryotic organisms. Profilin is important for spatially and temporally controlled growth of actin microfilame ...

s) in certain fruits and vegetables, which cross-react with pollen proteins.{{Cite journal , last=Cosme-Blanco , first=Wilfredo , last2=Arroyo-Flores , first2=Erving , last3=Ale , first3=Hanadys , date=2020-08-01 , title=Food Allergies , url=https://publications.aap.org/pediatricsinreview/article/41/8/403/35426/Food-Allergies , journal=Pediatrics In Review , language=en , volume=41 , issue=8 , pages=403–415 , doi=10.1542/pir.2019-0037 , issn=0191-9601{{rp, 409 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.{{dead link, date=September 2022 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 Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well. In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...

may be the underlying cause.{{Cite web , title=Oral Allergy Syndrome , url=http://www.aafa.org/display.cfm?id=9&sub=20&cont=728 , url-status=dead , archive-url=https://web.archive.org/web/20150905070132/http://www.aafa.org/display.cfm?id=9&sub=20&cont=728 , archive-date=2015-09-05 , access-date=2015-05-26 , website=Asthma and Allergy Foundation of America 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.{{Citation needed, date=March 2017

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 A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa''. In some countries, bananas used for cooking may be called "plantains", disting ...

watermelon Watermelon (''Citrullus lanatus'') is a flowering plant species of the Cucurbitaceae family and the name of its edible fruit. A scrambling and trailing vine-like plant, it is a highly cultivated fruit worldwide, with more than 1,000 varie ...

cantaloupe The cantaloupe, rockmelon (Australia and New Zealand, although cantaloupe is used in some states of Australia), sweet melon, or spanspek (Southern Africa) is a melon that is a variety of the muskmelon species (''Cucumis melo'') from the fami ...

, honeydew,

zucchini The zucchini (; plural: zucchini or zucchinis), courgette (; plural: courgettes) or baby marrow (''Cucurbita pepo'') is a summer squash, a vining herbaceous plant whose fruit are harvested when their immature seeds and epicarp (rind) are st ...

, and

cucumber Cucumber (''Cucumis sativus'') is a widely-cultivated creeping vine plant in the Cucurbitaceae family that bears usually cylindrical fruits, which are used as culinary vegetables.Alder Alders are trees comprising the genus ''Alnus'' in the birch family Betulaceae. The genus comprises about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few sp ...

pollen:

almond The almond (''Prunus amygdalus'', syn. ''Prunus dulcis'') is a species of tree native to Iran and surrounding countries, including the Levant. The almond is also the name of the edible and widely cultivated seed of this tree. Within the genu ...

apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ancest ...

celery Celery (''Apium graveolens'') is a marshland plant in the family Apiaceae that has been cultivated as a vegetable since antiquity. Celery has a long fibrous stalk tapering into leaves. Depending on location and cultivar, either its stalks, ...

cherries A cherry is the fruit of many plants of the genus '' Prunus'', and is a fleshy drupe (stone fruit). Commercial cherries are obtained from cultivars of several species, such as the sweet ''Prunus avium'' and the sour ''Prunus cerasus''. The ...

, hazel nuts,

peach The peach (''Prunus persica'') is a deciduous tree first domesticated and cultivated in Zhejiang province of Eastern China. It bears edible juicy fruits with various characteristics, most called peaches and others (the glossy-skinned, n ...

es,

pear Pears are fruits produced and consumed around the world, growing on a tree and harvested in the Northern Hemisphere in late summer into October. The pear tree and shrub are a species of genus ''Pyrus'' , in the Family (biology), family Rosacea ...

parsley Parsley, or garden parsley (''Petroselinum crispum'') is a species of flowering plant in the family Apiaceae that is native to the central and eastern Mediterranean region (Sardinia, Lebanon, Israel, Cyprus, Turkey, southern Italy, Greece, ...

raspberry The raspberry is the edible fruit of a multitude of plant species in the genus ''Rubus'' of the rose family, most of which are in the subgenus '' Idaeobatus''. The name also applies to these plants themselves. Raspberries are perennial with ...

strawberry The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid species of the genus '' Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The fruit is widely ap ...

{{cn, date=December 2022 *

Birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech- oak family Fagaceae. The genus ''Betula'' cont ...

pollen: apples, peach, pear, cherry.{{rp, 407

carrots The carrot (''Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in color, though purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild carrot, ''Daucus carota'', nati ...

, ,

chicory Common chicory (''Cichorium intybus'') is a somewhat woody, perennial herbaceous plant of the family Asteraceae, usually with bright blue flowers, rarely white or pink. Native to the Old World, it has been introduced to North America and Austra ...

coriander Coriander (;

fennel Fennel (''Foeniculum vulgare'') is a flowering plant species in the carrot family. It is a hardy, perennial herb with yellow flowers and feathery leaves. It is indigenous to the shores of the Mediterranean but has become widely naturalized ...

fig The fig is the edible fruit of ''Ficus carica'', a species of small tree in the flowering plant family Moraceae. Native to the Mediterranean and western Asia, it has been cultivated since ancient times and is now widely grown throughout the world ...

,{{cite journal , year=2003, title=Oral Allergy Syndrome to Fig, doi=10.1159/000070929, pmid=12811022, journal=International Archives of Allergy and Applied Immunology, volume=131, issue=2, pages=138–142 , last1=Antico , first1=A. , last2=Zoccatelli , first2=G. , last3=Marcotulli , first3=C. , last4=Curioni , first4=A., s2cid=19077935 hazel nuts,

kiwifruit Kiwifruit (often shortened to kiwi in North American, British and continental European English) or Chinese gooseberry is the edible berry of several species of woody vines in the genus ''Actinidia''. The most common cultivar group of kiwif ...

nectarine The peach (''Prunus persica'') is a deciduous tree first domesticated and cultivated in Zhejiang province of Eastern China. It bears edible juicy fruits with various characteristics, most called peaches and others (the glossy-skinned, n ...

, parsnips,

es,

pepper Pepper or peppers may refer to: Food and spice * Piperaceae or the pepper family, a large family of flowering plant ** Black pepper * ''Capsicum'' or pepper, a genus of flowering plants in the nightshade family Solanaceae ** Bell pepper ** Chili ...

plum A plum is a fruit of some species in ''Prunus'' subg. ''Prunus'.'' Dried plums are called prunes. History Plums may have been one of the first fruits domesticated by humans. Three of the most abundantly cultivated species are not found ...

potato The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae. Wild potato species can be found from the southern Uni ...

es,

prune A prune is a dried plum, most commonly from the European plum (''Prunus domestica''). Not all plum species or varieties can be dried into prunes. A prune is the firm-fleshed fruit (plum) of '' Prunus domestica'' varieties that have a high so ...

soy The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu and ...

strawberries The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid species of the genus '' Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The fruit is widely ap ...

wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

, jackfruit; ''Potential:''

walnuts A walnut is the edible seed of a drupe of any tree of the genus ''Juglans'' (family Juglandaceae), particularly the Persian or English walnut, ''Juglans regia''. Although culinarily considered a "nut" and used as such, it is not a true bot ...

{{cite web, title=It Might Be Your Allergies, url=https://www.rush.edu/health-wellness/discover-health/pollen-food-allergy-syndrome, website=Rush University Medical Center * Grass pollen:

melon A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. The word "melon" can refer to either the plant or specifically to the fruit. Botanically, a melon is a kind of berry, specifically a "pepo". T ...

tomato The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word ...

es, oranges,

* Mugwort pollen: carrots, celery, and

mustard Mustard may refer to: Food and plants * Mustard (condiment), a paste or sauce made from mustard seeds used as a condiment * Mustard plant, one of several plants, having seeds that are used for the condiment ** Mustard seed, seeds of the mustard p ...

{{rp, 407 * Ragweed pollen:

and melons ( honeydew,

),{{rp, 407

paprika Paprika ( US , ; UK , ) is a spice made from dried and ground red peppers. It is traditionally made from '' Capsicum annuum'' varietals in the Longum group, which also includes chili peppers, but the peppers used for paprika tend to be milder ...

, sunflower seeds/oil,

, echinacea,

artichoke The globe artichoke (''Cynara cardunculus'' var. ''scolymus'' ),Rottenberg, A., and D. Zohary, 1996: "The wild ancestry of the cultivated artichoke." Genet. Res. Crop Evol. 43, 53–58. also known by the names French artichoke and green articho ...

dandelions ''Taraxacum'' () is a large genus of flowering plants in the family Asteraceae, which consists of species commonly known as dandelions. The scientific and hobby study of the genus is known as taraxacology. The genus is native to Eurasia and Nor ...

honey Honey is a sweet and viscous substance made by several bees, the best-known of which are honey bees. Honey is made and stored to nourish bee colonies. Bees produce honey by gathering and then refining the sugary secretions of plants (primar ...

{{cn, date=December 2022

Diagnosis

The person typically already has a history of

atopy Atopy is the tendency to produce an exaggerated immunoglobulin E (IgE) immune response to otherwise harmless substances in the environment. Allergic diseases are clinical manifestations of such inappropriate, atopic responses. Atopy may have a ...

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. Those with OAS 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 Lactose intolerance is a common condition caused by a decreased ability to digest lactose, a sugar found in dairy products. Those affected vary in the amount of lactose they can tolerate before symptoms develop. Symptoms may include abdominal pai ...

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.{{citation needed, date=August 2020

Testing

Many people are unaware that they have OAS. However, if swelling,

tingling Paresthesia is an abnormal sensation of the skin (tingling, pricking, chilling, burning, numbness) with no apparent physical cause. Paresthesia may be transient or chronic, and may have any of dozens of possible underlying causes. Paresthesias a ...

or pain develops while eating certain foods, it is wise to see an allergy specialist. Before a diagnosis can be made, it is best to keep a food diary. This is important as the

physician A physician (American English), medical practitioner (Commonwealth English), medical doctor, or simply doctor, is a health professional who practices medicine, which is concerned with promoting, maintaining or restoring health through th ...

can then perform an allergy test. 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..{{citation needed, date=August 2020

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.{{citation needed, date=August 2020

Treatment

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.{{citation needed, date=August 2020

Antihistamine Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provide ...

s 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 Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands and ...

(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 those with 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.{{cite journal , date=December 2004, title=Effect of tree pollen specific, subcutaneous immunotherapy on the oral allergy syndrome to apple and hazelnut, journal=Allergy, volume=59, issue=12, pages=1272–1276, doi=10.1111/j.1398-9995.2004.00626.x, pmid=15507095 , last1=Bucher , first1=X. , last2=Pichler , first2=W. J. , last3=Dahinden , first3=C. A. , last4=Helbling , first4=A., s2cid=38141361

References

{{Reflist {{oral pathology Allergology Immune system disorders Otorhinolaryngology Syndromes