A. Case study
B. More information
C. Editors' comments
E. CPD questions (South Africa, Australia)
A. Case study
A 15-year-old girl
presented with swelling of the tongue and slight swelling of the throat
soon after ingestion of various types of food. The girl listed apple,
carrot, banana, peach and tomato as the offending foods. Her mother
had a severe peanut allergy. Because the mother experienced the first
symptoms of anaphylaxis to peanut as being swelling of the throat and
tightness of the chest, every time her daughter would start experiencing
swelling of the tongue and throat, the mother would encourage her to
take an antihistamine. The symptoms would then disappear within minutes.
The clinical history
revealed that the daughter had a history of hay fever as a result of
pollens. The pollen allergy started to present at age 7 when their neighbours
planted olive trees in their garden. The suspicion of pollen allergy
was arrived at by the child's mother because her daughter's symptoms
would appear specifically when the olive trees were pollinating. She
also sometimes experienced hay fever when she visited an area for the
first time. Sometimes olive trees were found to be present and other
times not. She took antihistamines to treat her hay fever as she needed
to. A doctor or allergist was never consulted about this. The girl started
developing reactions to foods later in life, when she was about 12 years
old. She decided to seek professional help when she started to react
to more and more of her favorite foods.
Upon further questioning,
the girl related that her throat started to itch just before it would
start to swell. She never experienced any difficulty breathing or any
other symptoms such as urticaria or eczema after eating the offending
This type of reaction is more likely to be an allergy than an intolerance.
What type of allergy reaction could this be?
a. Start of an anaphylactic reaction
b. Contact urticaria/angioedema due to the offending food
c. Contact urticaria/angioedema due to something else that was present
in her mouth with the food, e.g., cutlery
d. Oral allergy syndrome
a. Although swelling of the throat is often one of the first symptoms
of an anaphylactic reaction, this was probably not the case here. If
the reaction was the start of anaphylaxis, taking antihistamines would
probably have little effect on the progression of the symptoms. The
symptoms also never got worse than a slight swelling of the throat,
even after eating large amounts of the offending food.
b. The symptoms she described sounded similar to urticaria or angioedema.
Although contact allergy to these foods is possible, the girl did not
experience any swelling after contact of food with any other part of
c. The foods that would elicit a reaction were all eaten with her hands
or with cutlery. The cutlery was used to eat all her other food, without
d. The typical characteristics of oral allergy syndrome are:
i. Localized oropharyngeal
symptoms: These were present.
ii. Concomitant sensitization to a respiratory allergen: This was present
(olive tree pollen).
iii. Reproducible symptoms with repeated contact with a particular food.
The patient was asked the following questions: Did she always react
to a specific food whenever she ate it, without exception? Did she sometimes
react to raw but not cooked food? Was she eating the foods on their
own or mixed with other food?
Trying to determine
the foods that caused her symptoms, she had tried all the suspect foods
by themselves. The child reacted to all the foods every time she ate
them, except carrot and tomato. She was unsure whether she would react
to the foods if they were cooked, as she ate most of them raw. However,
she had picked up before that she reacted to carrot only when eaten
raw. She was not sure whether tomato was cooked or uncooked when she
reacted to it.
It was thus clear
that she was reacting to at least one heat-labile allergen.
Is there a common allergen in these foods that was causing them to cross-react
with each other? And is this allergen heat-labile?
Profilin, a heat-labile panallergen, was found to be present in all
of the foods that she listed. (Panallergens are allergens that are present
in a number of plants, including pollens. The plants are not necessarily
related to each other by family. Each panallergen performs a specific
function in the various plants.) This would explain why she did not
react to carrot when it was eaten cooked. All of the other foods were
generally eaten raw. A possible reason for her uncertainty about when
she reacted to tomato is that tomato can be eaten raw or cooked and
she had not picked up an association. In general, her experience suggested
that a sensitivity to profilin was causing her symptoms.
If this were oral
allergy syndrome, one would expect the same allergen to be present in
the pollen that was causing the respiratory symptoms (hay fever, in
her case). It was determined that profilin is also present in olive
tree pollen. It was thus clear that the girl was experiencing oral allergy
syndrome to apple, carrot, banana, peach and tomato, which can be concomitant
with respiratory allergy to olive tree pollen.
Oral allergy syndrome
rarely causes symptoms more severe than slight swelling of the throat,
but if the patient wanted to avoid this reaction, she would have to
avoid eating these foods, or she would have to cook them before she
ate them. She was also informed of other pollens, containing profilin
that she might react to, such as Bermuda grass, common silver birch
tree, date palm tree, European chestnut tree, hazelnut tree, Johnson
grass, mugwort, ragweed, Timothy grass and white ash tree.
|TIP for Allergy
When entering the offending foods into the pattern search
function of Allergy Advisor, a common constituent, profilin,
a panallergen, is identified. (The panallergen search function
can also be used.) When clicking on the word, a window will
open and allow the user to read more about profilin, including
that it is heat labile and that it can be associated with
oral allergy syndrome. Clicking on the "Cross-reactions"
tab along the top of the window, one will find details of
cross-reactions between these profilin-containing foods. Under
the "Management menu", one can find a list of foods
that have been associated with oral allergy syndrome (click
the "Differential Diagnosis Lists" button).
B. More information:
What is Oral Allergy
syndrome (OAS) is an IgE-mediated reaction to a certain food (or foods
that all contain a similar allergen), affecting the oropharyngeal mucosa
of sensitized individuals.1 Symptoms include itchiness (pruritus)
and swelling of the lips, tongue, palate and throat.2,3
What causes OAS?
OAS is caused by various types of fruit, vegetables and nuts. But what
makes this syndrome so distinctive is that it is always seen in individuals
with co-existing sensitization to inhaled allergens, usually tree, weed
or grass pollens. If symptoms to inhaled allergens are experienced,
they are most often those of hay fever.3,4 It should be noted that
there have been reports of OAS symptoms without a concomitant sensitization
to an inhaled allergen. But there is a question whether these cases
should be referred to as OAS or as "OAS-like symptoms," as
true OAS according to the definition is the combination of allergy to
food and to an inhalant allergen.
How common is
OAS appears to be more common in adults than children.5 Atopic individuals
are more prone to OAS, especially those who are sensitive to pollens.6
It has been reported to occur in up to 35-75% of patients with pollen
the association between pollen allergy and allergy to fruit and
This is explained by cross-reacting allergens, which means that
the same allergen is present in both pollen and fruit and/or vegetables,
even though they may not belong to the same botanical family.
The hypothesis is that a patient becomes sensitized to an airborne
pollen allergen (by gradually building up IgE antibodies to these
allergens over time) and then becomes capable of reacting to the
same allergen that is present in various foods.2,11,12,13,14
A number of
allergens have been associated with OAS, including lipid transfer
protein (heat-stable) and the profilin family (heat-labile), including
Bet v1 and Art v1.11 These are all panallergens and,
as indicated, are either heat-stable or heat-labile. Patients
affected by a heat-labile allergen may be able to tolerate the
foods containing it when these are cooked.2,11
are defense-related proteins, which provide a plant with resistance
to stresses (e.g., infections/viruses, harsh growing conditions
and exposure to some types of chemicals). Under stress conditions,
the defense-related proteins increase. Agriculturally, this property
in a plant could be quite valuable. Less toxic substances that
cause crops to express defensive proteins are being investigated
as a new type of agrochemical. This has important implications
for the allergenicity of future plants, as increasing the defense-related
proteins means that panallergen concentration also increases.15
A fairly well-known
example of another panallergen, which is not involved in OAS,
is chitinase. It is present in latex and foods such as kiwi and
mango and is responsible for the cross-reactivity between them.16
between food and pollen allergies that have been recorded include:
Birch: Almond, apple, apricot, carrot, celery, cherry,
fennel, hazelnut, kiwi, nectarine, parsley, parsnip, peach, pear,
plum, potato, prune and walnut
Ragweed: Banana, chamomile tea, cantaloupe, cucumber, dandelion
tea, honey dew, watermelon and zucchini
Mugwort: Apple, carrot, celery, coriander, fennel, melons,
pepper and sunflower
Grass: Melons, orange and tomato6
food and airborne allergens associated with OAS include:
Allergy to ingesting various kinds of pork (salami, bacon and both
raw and cooked ham), associated with an inhaled allergy to horse dander.
This person could, however, tolerate cooked pork (chops and sausages).
The allergy was due to a heat-labile allergen.17
Allergy to uncooked mushroom in a patient allergic to mold11
Allergy to pistachio nut and Parietaria (a type of weed)18
OAS after the ingestion of salami in a patient with sensitization
to dust mite allergens3
Allergy to fig,19 jackfruit,20 spinach,21
shell-fish, egg22 and chicken meat23
The type of concomitant
pollen and food sensitivity a person might experience is mainly dependant
on the immediate environment. For example, in Italy, where grass pollen
is a common cause of hay fever, one would expect OAS to be more often
associated with food allergy to tomato, melon, watermelon and orange,
all of which are widely consumed in that country.24
tend to be associated with different types of reactions. A person reacting
to Bet v1, for example, is likely to experience OAS alone. Those sensitive
to LTPs frequently experience both OAS and systemic symptoms after eating
an offending food.25
associated with OAS
Symptoms present during or within 5-30 minutes of oral contact
with the culprit food and generally resolve rapidly (within ½
- 1 hour).24
include itching of the lips, mouth or pharynx and angioedema (swelling)
of the lips, tongue, palate and throat. Blisters may also appear
in the oral area. (These must be distinguished from apthous ulcers,
which are not associated with OAS.) In severe cases, edema of
the glottis may occur. This occurs frequently in patients with
OAS due to celery.26 More and more cases of severe
reactions to celery are occurring, so much so that some European
countries consider it to be a major allergen.
symptoms are considered to be a distinct entity, they can extend
beyond oropharyngeal manifestations to systemic reactions in some
individuals, especially those who continue to ingest the offending
food. Symptoms include urticaria, angioedema, conjuctivitis, rhinitis,
asthma, nausea, vomiting and anaphylaxis. Anaphylaxis has been
reported in approximately 2% of patients with OAS. Foods implicated
in anaphylaxis associated with OAS include lentils, tomatoes,
apricot, peach, pear, cherry, apple, walnut and hazelnut.27
A thorough clinical history is the best tool to diagnose OAS. As
mentioned in the case study, the typical symptoms are:
reproducible with repeated contact with a particular food.
localized to the mouth, lips, pharynx and glottis.
accompanied by sensitization to an inhaled allergen.2
clinical history may be supported by allergy tests. The value
of skin prick tests is often limited in OAS, as the proteins (allergens)
in commercial extracts that are used (e.g., fruit extract) degrade
easily, leading to significant loss in potency and diagnostic
sensitivity and sometimes resulting in false negatives.2,14
This tends to be due to factors in the preparation of the extract,
such as heat. As discussed above, many patients who suffer from
OAS can tolerate cooked food but not the raw form.28
The efficiency of skin prick and blood tests as predictors of
clinical food reactivity varies depending on the type of food.
Although sometimes impractical and perhaps risky (because of the
chance of anaphylaxis), skin prick tests with fresh foods may
have greater diagnostic sensitivity.2,14
fresh fruits or vegetables are used, characteristics of the food
may, however, influence the sensitivity of the skin prick test.
For example, the allergenic potency may increase during the food's
maturation, as shown for Golden Delicious apples.29
Also, one should ensure that the patient does not react to other
compounds that are present in the extract. A example of this is
a histamine-sensitive individual who could show a reaction (non-allergic
reaction but similar to an allergic reaction) to fresh tomato
extract, which naturally contains histamine.
Another aid in the
diagnosis of OAS is to challenge the patient with the suspected food.
The results can then be compared to the characteristic symptoms of OAS
(listed above). The challenge should be done with the natural form of
the food. It must not be dried or given in capsule form.
The easiest, safest and cheapest treatment is avoidance of the food.
If the symptoms are due to a heat-labile allergen such as profilin,
the patient may tolerate cooked or canned food. Many of the panallergens
involved in OAS are found predominantly or exclusively in the skins
of the offending foods. Some persons may therefore prevent a reaction
by removing the skins. However, this is not an absolute guarantee of
safety, as the act of cutting or peeling may shift the proteins in the
skin to the flesh of the food.6 If a person does not wish
to avoid one or more foods, an antihistamine could suppress the resultant
The patient should
be warned of other foods and airborne allergens that may affect him
or her due to the presence of the same allergen (as was done in the
case study). For example, an apple-allergic individual living in the
Southern Hemisphere, where there are very few birch trees (which cross-react
with apple), should be warned of the presence of these trees when visiting
Europe. Airborne allergens that affect the patient can be avoided by
visiting certain areas at the times of the year when there is a low
pollen count. With regard to foods, one must keep in mind that people
may not react in the same way to all the foods containing the same allergen.
||compiled by Karen du Plessis
Food & Allergy Consulting & Testing Services (FACTS)
PO Box 565
Comments by our editor
M. Joneja Ph. D., RDN
OAS is becoming increasingly recognized as an allergic disease
distinct from anaphylaxis. The increased incidence of OAS may
be a result of better methods of diagnosis, or, as some researchers
suggest, a symptom of an increase in pathogenesis-related proteins,
which are important allergens common to trees and food plants
involved in the aetiology of OAS. Pathogenesis-related proteins
tend to be expressed by trees and plants under "stress"
as a result of pollution and other environmental agents that could
potentially harm the plant, and are thought to be a response to
the noxious chemicals that seem to be increasing in the urban
foods responsible for triggering OAS are sometimes difficult to
identify because they often do not elicit a typical response in
skin tests, as a result of the use of inappropriate allergen preparations.
A method of skin testing that is frequently employed in order
to avoid the false negative results common with commercial allergen
extracts, is the prick-to-prick method. In this test, a sterile
needle is inserted into the fresh, raw food, and then inserted
into the patient's skin. This transfers non-denatured antigen
and is more likely to elicit a positive response than a commercial
extract of the same food. However, even the prick-to-prick test
is not highly accurate, and diagnosis of the culprit food/pollen
combination in OAS must be confirmed by challenge. An obvious
danger of the prick-to-prick test is when the OAS is in fact part
of an anaphylactic reaction that has been misdiagnosed as OAS.
Transferring a raw antigen into the skin in an anaphylactic patient
can be fatal, so great care must be taken to avoid using this
suffering with OAS should remember that they are more prone to
developing symptoms of hayfever when going on holiday to other
parts of the world where specific trees (whose pollen shares cross-reacting
allergens) are more prevalent.
For more information
on this subject and other allergy and intolerance related topics, visit:
To join a professional
food allergy discussion list where this subject can be discussed further,
go to http://groups.yahoo.com/group/AllergyDietitian
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1. Amlot PL, Kemeny
DM, Zachary C, Parks P, Lessof MH. Oral allergy syndrome (OAS): symptoms
of IgE-mediated hypersensitivity to foods. Clin Allergy 1987; 17:33-38.
2. Ortolani G, Ispano M, Pastorello EA, Ansaloni R, Magri A. Comparison
of results of skin prick tests (with fresh foods and commercial extracts)
and RAST in 100 patients with oral allergy syndrome. J Allergy Clin
Immunol 1989; 83: 683-690.
3. Liccardi G, D'Amato M, D'Amato G. Oral allergy syndrome after ingestion
of salami in a subject with monosensitization to mite allergens. J Allergy
Clin Immunol 1996;98:850-2.
4. Helbling A. [Important cross-reactive allergens] Schweiz Med Wochenschr.
1997 Mar 8;127(10):382-9.
5. Kivity S, Dunnerk K, Marian Y. The pattern of food hypersensitivity
in patients with onset after 10 years of age. Clin Exp Allergy 1994;
6. Sloane D, Sheffer A. Oral allergy syndrome. Allergy Asthma Proc.
7. Bircher AJ, Van Melle G, Haller E, Curty B, Frei PC. IgE to food
allergens are highly prevalent in patients allergic to pollens, with
and without symptoms of food allergy. Clin Exper Allergy 1994; 24:367-374.
8. Pastorello EA, Ispano M, Pravettoni V et al. Clinical aspects of
food allergy. Proc XVI European Congress of Allergology and Clinical
Immunology 1995; 883-888.
9. Eriksson NE. Birch pollen allergy associated with food hypersensitivity.
An enquiry study Nordic Aerobiology 1984; 66-69.
10. Ebner C, Birkner T, Valenta R et al. Common epitopes of birch pollen
and apples. Studies by Western and Northern blot. J Allergy Clin Immunology
11. Dauby PL, Whisman BA, Hagan L. Cross-reactivity between raw mushroom
and molds in a patient with oral allergy syndrome. Ann Allergy Asthma
12. Eriksson NE. Clustering of foodstuffs in food hypersensitivity.
An enquiry study in pollen allergic patients. Allergol Immunopathol
13. De Martino m, Novembre E, Cozza G, et al. Sensitivity of tomato
and peanut allergens in children monosensitized to grass pollen. Allergy
1988; 43: 206-213.
14. Anhoj C, Backer V, Nolte H. Diagnostic evaluation of grass- and
birch-allergic patients with oral allergy syndrome. Allergy 2001;56:548-52.
15. Yagami T. Allergies to cross-reactive plant proteins. Latex-fruit
syndrome is comparable with pollen-food allergy syndrome. Int Arch Allergy
Immunol. 2002 Aug;128(4):271-9.
16. Brehler R,Theissen U,Mohr C, Luger T. "Latex-fruit syndrome":
frequency of cross-reacting IgE antibodies. Allergy 1997;52(4):404-10.
17. Asero R, Mistrello G, Falagiani P. Oral allergy syndrome from pork.
18. Liccardi G, Mistrello G, Noschese P, D'Amato M, D'Amato G. Oral
allergy syndrome (OAS) in pollinosis patients after eating pistachio
nuts. Two cases with two different patterns of onset. Allergy 1996;51:919-22.
19. Antico A, Zoccatelli G, Marcotulli C, Curioni A. Oral allergy syndrome
to fig. Int Arch Allergy Immunol 2003;131(2):138-42.
20. Wutrich B, Borga A, Yman L. Oral allergy syndrome to jackfruit (Artocarpus
integrifolia). Allergy 1997;52:428-31.
21. Sanchez I, Rodriguez F, Garcia-Abujeta JL, Fernandez L, Quinones
D, Martin-Gil D. Oral allergy syndrome induced by spinach. Allergy 1997;52:1245-6.
22. Joneja JM. Oral allergy syndrome, cross-reacting allergens and co-occurring
allergies. Journal of Nutritional & Environmental Medicine 1999;9:289-303.
23. Vila L, Barbarin E, Sanz ML. Chicken meat induces oral allergy syndrome:
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24. Ortolani C, Ispano M, Pastorello EA, Bigs A, Ansaloni R. The oral
allergy syndrome. Ann Allergy 1988; 61: 47-52.
25. Asero R. Detection and clinical characterization of patients with
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MC. Celery allergy: clinical and biological study of 20 cases. Ann Allergy
1988; 60: 243-246.
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from vegetable allergens. Ann Allergy 193; 83: 683-690.
28. Wutrich B, Staeger J, Johansson SGO. Celery allergy associated with
birch and mugwort pollinosis. Allergy 1990; 45: 566-571.
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Questions (For South African dietitians only. Australian
dietitians: where you have relevant learning goals, CPD hours related
to this resource can be included in your APD log.)
You can obtain 2 CPD points for reading
this newsletter and answering the accompanying questions. This
newsletter with questions has been accredited for dietitians.
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ALL THE QUESTIONS
(There is only
one correct answer per question.)
1. What type of
reaction is Oral allergy syndrome (OAS)?
(d.) Toxic reaction
2. Which of the
following panallergens would not be tolerated when cooked?
(b.) Bet v1
(c.) Art v1
(d.) Lipid transfer protein
3. Plant defense-related
proteins provide protection against which of the following?
(a.) Plant infections/viruses
(b.) Harsh growing conditions
(c.) Exposure to chemicals
(d.) All of the above
4. Which one of
the following is not a typical example of allergens that would be concomitantly
involved in OAS?
(a.) Birch, apple and celery
(b.) Ragweed, plum and apricot
(c.) Mugwort, apple and celery
(d.) Grass, melon and tomato
5. Which of the
following is true regarding the onset and resolution of OAS symptoms?
(a.) Onset: 5-30 minutes; Resolution: ½ - 1 hour
(b.) Onset: 1 hour; Resolution: 2-4 hours
(c.) Onset: 2 hours; Resolution: 5-10 hours
(d.) Onset: 1 day; Resolution: 2-2.5 days
6. Which of the
following does not fit the TYPICAL presentation of OAS?
(a.) The symptoms are reproducible with repeated contact with a particular
(b.) The symptoms are localized to the mouth, lips, pharynx and glottis.
(c.) Sensitization to an inhaled allergen is present.
(d.) Systemic manifestations are present.
7. True or false:
The value of skin prick tests with commercial extracts is limited in
the diagnosis of OAS, as the proteins (allergens) degrade easily.
8. True or false:
The easiest, safest and cheapest treatment of OAS is with antihistamines.
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