A. Case study
B. More information
C. Editors' comments
E. CPD questions (South Africa, Australia)
A. Case study
An 11-month-old boy was seen for eczema. Since birth he had been given
cow's milk-based formula, until he developed eczema at the age of 3
months. He was put onto a soya formula, and his symptoms resolved. The
mother began to give him solid foods at age 5 months. She started him
on rice and maize cereals and gradually introduced a variety of fruits
and vegetables, as well as rice, potato, chicken and beef. At the age
of 9 months, he developed severe eczema again. He was drinking about
800ml of soya formula per day at this stage. The general practitioner
requested some blood tests, with the following results (in KU/L):
Total IgE: 300 (High)
Soya: 9.47 (Class 3)
Rice: 0.39 (Class 1)
Maize: <0.35 (Class 0)
Potato: <0.35 (Class 0)
Phadiatop: 0.46 (Class 1)
(This last is a
screening test that measures the level of IgE to a combination of the
common inhalant allergens. A positive result indicates that the subject
is sensitized to 1 or more of these inhalants, but does not indicate
which. From there one can test for specific allergens.)
The mother was asked
to stop feeding with the soya formula, but the symptoms improved only
slightly. (She was, importantly, sent to a dietitian to ensure that
the child's diet would be nutritionally adequate.) The mother returned
to the doctor when the child was 11 months old. He still had chronic
eczema, but he also seemed to have severe "flare-ups" now
and again. The mother could not establish what the cause was.
Apart from reacting to something in his everyday environment or diet
that produced constant eczema, the child must have been exposed to something
causing the "flare-ups." What were the possibilities?
a. He was reacting to something (environmental or dietary) that he was
exposed to only occasionally.
b. He was sometimes being exposed to a higher dose of the allergen (environmental
or dietary) that was causing his constant eczema.
c. He was reacting to varying "hidden" sources of cow's milk
and/or soya in his diet.
d. In a patient with eczema, one should consider stress and other non-food
factors (e.g., exposure to house dust mite, pets, smoke, perfumes and
fabric softeners) that could aggravate eczema.
a-b. These will be discussed below.
c. A detailed dietary history was taken to determine whether hidden
allergens were present. But because the mother was very careful, she
gave only plain food (no processed foods or added flavorants). No hidden
allergens could be identified.
d. Even though the serum-specific IgE to Phadiatop was quite low, the
child could have been reacting to an environmental allergen not tested
for in the Phadiatop mix. No association could, however, be drawn between
any environmental allergen and his symptoms. The boy was not exposed
to smoke, perfumes or fabric softeners, and stress was not a factor.
What could be the next step?
a. Do more serum-specific IgE tests to other foods.
b. Ask the mother to keep a food-symptom diary.
c. Do an elimination diet and oral challenges.
a. There was no clear indication of which food could be a cause of the
reaction, and it would therefore have been difficult to suggest which
foods to test for. But testing for the most common allergens can be
helpful in such circumstances, as the chance of a child reacting to
one of these is better than to uncommon foods. The tests were done and
b. The purpose of keeping a diary is to detect a pattern in what is
eaten and the development of symptoms. Because the child experienced
constant eczema, the diary would probably not have assisted in identifying
the general cause; but it was potentially helpful for identifying the
allergen causing the "flare-ups." But it was decided to do
an elimination diet with challenges, which could be useful in both areas.
c. Because there was no clear indication of which food could be the
cause of the reaction, an elimination diet was singled out as an approach.
The mother was asked to allow only rice and rice products, maize and
maize products, potato (as the IgE levels of all of these were 0 or
low), banana, pear and chicken (as these are low-allergenic foods) in
her son's diet. The plan was to keep him on this diet until his symptoms
disappeared, and then challenge him with the foods that were excluded,
to see which provoked a reaction. After 1.5 weeks, the symptoms had
not improved. The mother did, however, pick up that her son's symptoms
got worse ("flared up") after he ate sweet corn. She was asked
to exclude all sources of maize, including the maize cereal, while still
following the rest of the elimination diet. This was done, and his symptoms
improved dramatically. Upon a rechallenge (with a double-blind method),
the symptoms flared again. This supports a recent finding that skin-specific
IgE and serum-specific IgE to maize have little, if any, clinical significance
for most patients studied (discussed below).
The other foods
were put back into his diet without adverse effects.
|TIP for Allergy
Allergy Advisor contains a guide to elimination diets under
the "Assessment" bar, under "Assessment Forms
& Guides". It contains examples of few foods diets
for different age groups as well as a step-by-step guide to
oral challenges. The "Challenge Vehicles" provides
ideas for vehicles that can be used to disguise foods during
B. More information:
Corn and maize
are terms used for the same plant, with the Latin name Zea mays.
For the purpose of this review, the term "maize" will
can occur to the ingestion of maize or maize derivatives, or to
the inhalation of maize flour or maize pollen. A true allergy
to maize has been said to be uncommon,1 but recent
studies have shown that diagnostic methods used in the past may
not have been accurate, so that maize allergy was underdiagnosed.
Also, the prevalence of this allergy may be higher in countries
such as Africa and Central and South America, where maize is a
An allergy to maize
may result in mild to severe reactions. Although anaphylactic reactions
to maize are uncommon, they can occur.9,10 An anaphylactic
reaction has even occurred during double-blind, placebo-controlled maize
challenges.11 One of the allergens in maize, Lipid Transfer
Protein (LTP, a panallergen), is reported to be responsible for this
severe form of allergic reaction.12 Food-dependant exercise-induced
anaphylaxis to maize has also been described.13 In a study
reporting on 7 cases of food-dependant exercise-induced anaphylaxis,
responsible foods were wheat (2 cases), maize, barley, shrimp, apple,
paprika and mustard.14
Anaphylaxis to maize
starch glove powder has been described in 2 nurses. The authors suspected
that cornstarch was the responsible allergen.15 Other adverse reactions
that have resulted from cornstarch surgical glove powder include contact
urticaria, oculorhinitis, angioedema, asthma and intermittent episodes
of dyspnoea.16,17,18 Cornstarch powder in medical gloves also plays
an important role in latex-induced hypersensitivity, as an allergen
carrier by the inhalation route, by skin contact or by direct contact
with mucous membranes, so that the powder can enhance latex-induced
including dermatitis, have been described with maize by-products, corn
syrup, corn dextrimaltose, corn invert sugar, corn isomerised dextrose
and corn D-psicose.20,21,22 This demonstrates that one or more allergens
remain in maize throughout processing and are still present in maize
derivatives. Intravenous administration of a maize-derived dextrose
solution has resulted in anaphylaxis. Symptoms included oro-facial swelling,
difficulty in breathing, hypotension, cardiac arrhythmia, voice hoarseness,
total body warmth and flushing. These reactions occurred within 8 minutes
of initiation of a 5% dextrose Lactated Ringer's solution.23
There has been a
report of hypersensitivity reactions to the ceremonial use of oral maize
pollen among Native Americans. The symptoms included various combinations
of oral and ear itching, sneezing, cough, and wheezing.24
Other allergic symptoms
from oral ingestion that have been reported include abdominal pain,
nausea, vomiting, atopic dermatitis,3 oral allergy syndrome4 and
recurrent serous otitis media.25 Maize has also been reported to cause
In the occupational
Occupational exposure to maize, maize flour or maize dust may result
in occupational asthma or rhinitis, in particular in bakery workers,
mill workers and those working in the animal feed industry.3,27,28,29,30
As discussed above, contact urticaria and anaphylactic reactions can
occur from cornstarch surgical glove powder.15 Whether atopy may play
a role in the development of grain dust-induced airway disease has not
been fully evaluated yet.27 In a group of 35 men working in an animal
food processing plant, the most frequent positive skin prick reactions
occurred to the following occupational allergens: fish flour (82.9%),
carotene (77.1%), maize (65.7%), four-leaf clover (62.9%), sunflower
(54.3%), chicken meat (31.4%), soy (28.6%), and yeast (22.7%).29
have been identified
Many allergens have been isolated from maize, but the majority of them
have not been clinically evaluated for their allergenic potential. The
most researched allergen is Zea m 14, a LTP, that was isolated from
maize flour.2,9,12,31,32,33 It is a major maize allergen.9 Maize
LTP maintains its IgE-binding capacity after heat treatment, which makes
it the most likely allergen responsible for severe anaphylactic reactions
to both raw and cooked maize.34
present in maize (but with allergenic potential not yet evaluated) are
The maize inhibitor of trypsin (it cross-reacts with grass, wheat,
barley, and rice trypsin inhibitors);9
A 22 kDa protein from maize seed, with a 52% homology with the
protein thaumatin, and a 99% homology with the 22 kDa trypsin/alpha-amylase
A protein similar to an isoflavone reductase (a panallergen,
and a plant defence protein) and/or an isoflavone reductase-like protein;36
A chitinase.37 There are various chitinases, of which only
some are allergenic.
protein (the protein found in cereals that causes the same intestinal
damage in Celiac Disease that gliadin, found in wheat, causes)
in maize is called zein. Prolamin contributes 55% to the grain's
protein content, but the ingestion of maize is considered safe
in Celiac Disease.3,38
two basic types of maize, namely sweet corn and field corn. Sweet
corn is distinguished from field corn by the high sugar content
of the kernels at the early "dough" stage and by wrinkled,
translucent kernels when dry.However, cultivars of maize may also
be divided into six types: popcorn (everta), flint corn (indurata),
dent corn (indenta), flour corn (amylacea), sweet corn (saccharata)
and pod corn (tunicata). Even though they may look different,
cultivated hybrids of maize are from the same species and there
are no differences in their protein profile and allergenic properties.34
Individuals with allergy to maize pollen may also demonstrate allergy
to maize seed, as both contain similar allergens.32,39 In
a group of 56 children with hay fever as a result of maize pollen, more
than half were sensitized to maize seed allergens.39
belongs to the family Poaceae (Gramineae); other members include
sorghum, oats, rice, barley, rye, wheat and various grasses. One
would expect there to be an extensive cross-reactivity among these
individual species of the genus, but there appears to be a low degree
of cross-reactivity between maize and other cereals.40
However, by using RAST inhibition tests, the degree of cross-reactivity
between cereal grains was shown to closely parallel their taxonomic
relationship and appeared to be in the following order of decreasing
closeness: wheat, triticale, rye, barley, oat, rice and corn.41
Another study showed that there were significant close correlations
between every combination of RAST values for rice, wheat, corn,
Japanese millet and Italian millet.42
Also, in vitro cross-reactivity
among the IgE binding proteins of maize, rice, soybean and peanut has
been demonstrated,43 and the maize inhibitor of trypsin cross-reacts
with grass, wheat, barley, and rice trypsin inhibitors.9
The relevance of these cross-reactions (above) still needs to be established
from a clinical perspective. Cross-reactions in foods (including maize)
containing LTP have been reported to be more clinically relevant. A
high degree of cross-reactivity has been demonstrated among the LTP's
of maize, peach, apple, walnut, hazelnut, peanut, rice, and apricot.9,44,45
Not all LTP's from plants are, however, closely related.46
For example, maize LTP was shown to cross-react completely with rice
and peach LTP but not with wheat or barley LTP. Overall, there is a
low cross-reactivity between maize LTP and the LTP's of other cereals.9
There appears to
be an unidentified but common allergen in birch pollen and apple, pear,
carrot, banana and other exotic fruits. The clinical relevance, again,
has not been established.36
methods can be used?
Traditionally, skin-specific and serum-specific IgE tests to maize are
used to diagnose maize allergy. It is generally assumed that a negative
result indicates the absence of maize allergy. However, it was recently
shown that a negative skin-specific IgE and serum-specific IgE to maize
flour had no clinical significance for most of the patients studied,
and that food allergy to maize has to be proved by double-blind placebo-controlled
food challenge studies.3
Because maize is
eaten in various ways (as a vegetable, or as derivatives of maize in
the form of corn oil, corn syrup, cornstarch, corn flour, and cornmeal)
and the specific allergen profile of various maize derivatives is not
known, it may be necessary to challenge each derivative separately.
Each derivative may have a different potential for triggering adverse
reactions. It is therefore useful to assess a person's tolerance of
each component. If some maize derivatives are proven to be safe, it
will improve dietary variety, especially in severely allergic individuals.47
Maize elimination diets are very difficult to manage because maize and
maize products constitute ingredients in a large number of processed
food products, especially snack foods.1,47
Maize is likely
to be present in foods containing the following ingredients: corn, cornmeal,
cornflakes, cornmeal, corn sweetener, corn syrup solids, corn flour,
corn starch, caramel corn, maize, corn alcohol, baking powder, dextrates,
dextrins, flavouring (caramel, both natural and artificial), maltodextrins,
marshmallow, powdered sugar, hominy, grits, popcorn, vegetable gum,
vegetable paste, food starch, modified starch, vegetable starch, vegetable
protein and starch. Hydrolysed plant protein (HPP), hydrolysed vegetable
protein (HVP) and textured vegetable protein (TVP) may also be made
from maize. Even though, as with similar products derived from wheat,
it is known that the hydrolysis process breaks down proteins to the
point where they are unlikely to be allergenic,1,47 insufficient knowledge
about the allergens in maize makes it impossible to ensure that all
allergens will be broken down to the point at which a substance may
be freely included in the diet.
In the processing
of maize oil, the protein is removed. The oil could therefore be seen
as safe for consumption.1 However, the product may become contaminated
with protein from maize during manufacturing. It is probably not necessary
to restrict maize oil as an ingredient in foods, as maize protein is
an uncommon cause of anaphylaxis and the quantity likely to be present
in the oil depends on the processing and might be very small.47
In the highly maize-allergic
individual, eliminating maize entirely from the diet would require the
exclusion of a variety of foods, including non-alcoholic beverages,
candy, canned fruits, cereals, cookies, jams, jellies, lunch meats,
snack foods, syrups, convenience foods and infant formulas.1,3,47
Whiskey, beer, and other alcoholic beverages may also have to be excluded,
as they may be produced using maize. It has been demonstrated that LTP
in barley is one of the main allergens responsible for allergic reactions
In spite of
the wide use of maize in food manufacturing, eliminating maize
from one's diet would not normally lead to nutritional deficiencies.
Exceptions would occur in countries where maize is a staple food
and alternatives are too expensive or not available. Normally,
if a person's usual diet contains many maize-containing convenience
foods, alternative maize-free products can be suggested.1,47
ingredients can be used (probably more commercially than domestically)
as alternatives to maize derivatives:
Sweeteners: fruit juice, honey, beet sugar, cane sugar and maple
Thickeners: rice starch, potato starch, tapioca and wheat starch;
Leavening agents: baking soda and cream of tartar (5 ml or 1
tsp baking powder can be replaced by 1 ml or ¼ tsp bicarbonate
of soda and 2 ml or ½ tsp of cream of tartar).1
||compiled by Karen du Plessis
Food & Allergy Consulting & Testing Services (FACTS)
PO Box 565
Comments by our editors
Janice M. Joneja Ph. D., RDN
It has been
my experience through many years of managing food allergies and
intolerances that adverse reactions to corn and corn derivatives
are frequently undiagnosed, and the incidence of corn allergy
is greatly underestimated. Because skin tests and tests for anti-corn
antibodies in blood are generally negative, the assumption that
corn allergy is uncommon has been made to the detriment of many
corn-sensitive individuals - usually children. As this case study
demonstrates, corn allergy is an example of a food allergy that
can only be successfully and accurately identified by elimination
and challenge. Corn is not unique in this respect since allergy
to a number of foods is often overlooked because the standard
allergy tests are negative. We have to keep in mind that because
of the high incidence of false negative, and sometimes false positive
results, estimates of the efficacy of skin and blood tests for
food allergy never exceed 50%, and many practitioners rate them
even lower. Even when a positive skin or blood test indicates
the presence of anti-food IgE, elimination and challenge must
be undertaken to demonstrate that the food does in fact cause
clinical symptoms when it is consumed. It is more than probable
that factors other than the presence of IgE (and/or IgG) antibodies,
and reactive immune cells in the skin, are responsible for the
expression of allergy. Until science is able to elucidate the
precise mechanisms responsible for all types of clinical allergy,
we must rely on carefully controlled elimination and challenge
to accurately identify the foods responsible for the symptoms
more information on this subject and other allergy and intolerance related
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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Questions (For South African dietitians only. Australian
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PLEASE ANSWER ALL THE QUESTIONS
(There is only one correct answer per question.)
1. Which of the following has been associated with an adverse reaction?
(a.) Maize flour
(b.) Maize pollen
(c.) Maize starch glove powder
(d.) All of the above
2. Which of the
following is not true regarding anaphylactic reactions to maize?
(a.) They are uncommon.
(b.) They are likely to be caused by Lipid Transfer Protein.
(c.) They can be precipitated by exercise, i.e., as food-dependant exercise-induced
(d.) They cannot occur due to a double-blind placebo-controlled challenge
3. Which of the
following adverse reactions has been associated with maize starch glove
(b.) Contact urticaria
(d.) All of the above
4. True or false:
Occupational exposure to maize, maize flour, or maize dust may result
in occupational asthma or rhinitis, in particular in bakery workers,
mill workers and those working in the animal feed industry.
5. True or false:
Even though popcorn and sweet corn are from the same species of maize,
their protein profile and allergenic properties are different. Their
allergenicity in the maize-allergic individual should therefore be evaluated
6. True or false:
There is a high degree of clinical cross-reactivity between maize and
7. Which is the
most accurate method of diagnosis of maize allergy?
(a.) Skin-specific IgE to maize
(b.) Serum-specific IgE to maize
(c.) Double-blind placebo-controlled challenge
(d.) None of the above
8. True or false:
Corn oil is likely to be safe for consumption in maize-allergic individuals.
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CPD Reference number: DT04/3/030/13
HPCSA number: DT
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