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There are a
number of groups of foods that are responsible for causing the
majority of food allergies. The list below gives some
information on these allergens. The list of foods for which
allergies have been reported is much longer. A more
comprehensive list can be obtained from
Food Allergy Network or
visit the Anaphylaxis
Campaign and view their list of food warnings. This carries
info on all the latest warnings released by manufacturers (UK)
about peanut and other accidental cross contamination Cow's Milk:
Two out of
a hundred infants under one year old suffer from cow's
milk allergy, making it the most common food allergy of
childhood. In general children lose this sensitivity as
they grow up with nine out of ten losing it by the age of
three; it is unusual for adults to suffer from this
allergy.
Symptoms
are frequently vomiting and diarrhoea in children, with
30-50% also having skin rashes of some type. A
small number of children have an anaphylactic reaction to
milk which tends to be lifelong.
The major
allergens in milk are the caseins and the whey protein b
-lactoglobulin. People are usually allergic to more than
one kind of milk protein.
The
proteins from cow's milk are very similar to those
from goats and sheep, and can cause the same sorts of
reaction in cow's milk-allergic subjects. Thus goat's
or sheep's milk cannot be used as a cow's milk substitute
in allergic individuals.
Eggs: Allergy to
eggs is usually observed in young children rather than
adults, and like cow's milk allergy, fades with time.
Occasionally children suffer from a severe form of allergy
which is not outgrown. The main
allergens are the egg white proteins ovomucoid, ovalbumin,
and ovotransferrin.
The eggs of
other poultry, such as ducks, are very similar to those of
hens and can cause reactions in egg-allergic individuals.
Fish and
shellfish: Allergies
to shellfish are unusual in children, mostly being
experienced by adults. Reactions to fish are found in
children and adults. The incidence of seafood allergy is
higher in those countries with a high consumption of fish
and shellfish.
Severe
reactions are more frequently found with these foods,
including anaphylaxis. Cooking
does not destroy the allergens in fish and shellfish, and
some individuals maybe allergic to the cooked, but not
raw, fish.
The major
allergens in fish are flesh proteins called parvalbumins
which are very similar in all kinds of fish. This is why
people allergic to cod tend to be allergic to fish such as
hake, carp, pike, and whiting as well.
Shellfish
allergens are usually found in the flesh and are part of
the muscle protein system, whilst in foods such as
shrimps, allergens have also been found in the shells.
Fruits: In general
allergic reactions to fruits and vegetables are mild, and
are often limited to the mouth, and are called the
oral-allergy syndrome (OAS). Around four
out of ten people having OAS are also allergic to tree and
weed pollens. Thus people who are allergic to birch pollen
are much more likely to be allergic to apples.
There
allergens in fruits and vegetables are not as complicated
as other foods. Many of them are very like the allergens
in pollens, which is why people with pollen allergies are
also allergic to certain fruits. Many fruit
allergens are destroyed by cooking, and thus cooked fruits
are often safe for fruit allergic people to eat.
Allergies
to latex gloves, especially amongst health professionals,
are increasing. As many of the latex allergens are like
those found in certain tropical fruits, such as bananas,
these people can get an allergic reaction to handling or
eating these foods .
Legumes: This group
of foods includes soya beans and peanuts. Peanuts are one
of most allergenic foods and frequently cause very severe
reactions, including anaphylaxis.
Allergy to
peanuts is established in childhood and usually maintained
throughout life. Both these
foods have multiple allergens which are present in the raw
and cooked foods.
Peanut
allergy can be so severe that only very tiny amounts of
peanut can cause a reaction. Thus the traces of nuts found
in processed oils, or the carry over of materials on
utensils used for serving foods, can be enough in some
individuals, to cause a reaction.
The main
allergens in peanuts and soya are the proteins used by the
seed as a food store for it to grow into a seedling. One
of the allergens in soya bean is very similar to a major
allergen from dust mites, a common environmental allergen.
We aren't sure yet whether this means there is a link
between dust allergy and soya allergy.
Tree nuts: This group
includes true tree nuts, such as Brazil nuts, hazelnuts,
walnut and pecan.
Whilst not
as intensively studied as peanuts, indications are that
tree nuts can cause symptoms as severe which can
occasionally be fatal. Children
who become sensitised to tree nuts tend to remain allergic
throughout life.
Hazelnut
and almond allergies are more like those people get to
fruit, and are linked to pollen allergies. Nut
allergens can be both destroyed by, or resistant, to
cooking and we think that roasting may actually create new
allergens.
The
allergens can be the seed storage proteins, or other
molecules which are also found in pollen.
Cereals: Suffered by
children and adults alike, wheat allergy appears to be
particularly associated with exercise-induced anaphylaxis.
The more of
a cereal (wheat, rye, barley, oats, maize or rice) we eat
the more likely we are to suffer an allergy. Thus rice
allergy is found more frequently in populations eating
ethnic diets. Seed
storage proteins (such as wheat gluten) and other proteins
present in grain to protect it from attack by moulds and
bacteria, have been found to be major allergens.
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