Food Allergy - Specific Foods
Cows
milk allergy (dairy allergy)
Around 1 % infants have an allergy
to dairy products. Symptoms are often first experienced
when a baby is weaned and put onto cow's milk formula. Patients
are allergic to proteins (not fat) in the milk, and so all dairy
products should be avoided. Some parents give their children cows
milk substitutes, but be warned: 20 % of such children will be
allergic to soy milk as well, almost all will be sensitive to
goats milk and many are sensitive to horse milk too! Complete
avoidance is difficult, not only because milk products are used
in many processed foods (e.g. margarine, vegetarian cheese, crumbed
meats in batter, sausages, pastries, some baby foods, custards,
coffee whiteners, "dairy-free" desserts and so on),
but because it may appear on labels under different names like
casein, sodium caseinate, whey powder, cheese protein, milk,
non-fat milk solids, milk solids or lactose.
Soy allergy
This is also a common allergy of infancy,
often first experienced when a baby is given soy milk formula
because of known cows milk allergy. Like milk, it is hard to avoid
because it finds its way into so many processed foods like baked
goods such as bread, batters, cereals, sausages, as a binder in
small goods as well as in salads and canned beans. Soy lecithin
is an emulsifier (322) found in many foods such as chocolate,
margarine, and carob. Occasionally, very soy-sensitive subjects
will have reactions to this as well. Other names for soy include
soya, soy flour, soya protein, vegetable gum, textured vegetable
protein, hydrolysed vegetable protein, lecithin, bean curd, soya
bean paste (Miso, Tempeh), and tofu.
Egg allergy
Around 1 % infants have an allergy
to egg. The allergens are in the egg white as well as the egg
yolk and so both should be avoided. Those allergic to chicken/hen
eggs are usually allergic to other bird eggs such as duck eggs.
Common foods containing egg include malted drinks, custards, soufflés,
meringues, mousse, glazed rolls or pastries, some soups and sauces
(e.g. Hollandaise), rissoles or meat loaf (used as a binding agent),
cakes and slices, macaroons, dessert mixes (waffles, pavlova mix,
confectionery etc). Use of terms such as egg yolk and egg white,
albumen, egg powder or solids on the label may indicate the presence
of egg in a food. Cooked egg is sometimes better tolerated than
raw egg as cooking can partially destroy the allergen that causes
problems. Occasional patients are also allergic to chicken meat.
Peanut allergy and allergic reactions to
tree nuts
It is hard to avoid peanuts and tree
nuts completely because of their widespread use in processed foods,
and accidental exposure is common. Typical symptoms include facial
swelling, hives or vomiting. Types of foods containing peanuts
include peanut butter, mixed nuts, some Asian foods, shop-purchased
slices or cakes, biscuits, some cereals, chocolates, muesli or
health bars. Even though food labels are supposed to indicate
the presence of nuts, cross-contamination with traces of nuts
can be enough to trigger an allergic reaction. Some manufacturers
will also label their products as possibly containing traces
of nuts because multiple products may be made on the same production
line. The risk of cross-contamination is such circumstances is
probably low, but certainly not zero. Less commonly, nut products
or oils are used as unlabeled ingredients in cosmetics or massage
oils. The term Arachis oil, for example, means that peanut
oil is present. Around 50 per cent of those allergic to peanut
will have allergic reactions to tree nuts (such as almond, cashew,
hazelnut, walnut etc). Because of the risk of cross-contamination,
substitution and confusion, advice is often given to avoid all
nut-like foods. Only around 20 % of those with nut allergy will
ever grow out of it.
Seafood allergy
Seafood allergy
includes allergies to "scaly fish" and to crustaceans
like crab, prawns or lobster. Seafood allergy is uncommon in children,
but when it does occur, usually remains as a life-long problem.
Patients are usually allergic to 1 or 2 proteins that may be present
in multiple species. Allergy to one fish often results in allergy
to most other fish in the same way that allergy to one crustacean
usually means that all must be avoided.
Meat allergy
Meat allergy is uncommon. A large number of proteins in meat (including
collagen / gelatin) have been described as potential meat allergens.
Many patients allergic to beef are sensitive to similar proteins
present in lamb, and sometimes cows milk as well. Some patients
allergic to meat are able to tolerate the same food if it is well
cooked.
Wheat allergy
Allergic reactions to wheat and other cereals are most common
in infants and usually resolve within the first few years of life.
Whilst some children develop hives, other common symptoms are
those of worsening eczema. This usually occurs within a few hours
of eating. Occasionally delayed reactions occur after the food
is eaten regularly over several days, resulting in eczema or sometimes
diarrhoea or poor weight gain. In this situation, skin allergy
testing is often negative and the diagnosis rests on temporary
elimination from the diet followed by deliberate challenge under
careful medical supervision.
Wheat and cereal allergy is occasionally seen for the first time in adults. Many suffer from grass pollen hay fever as well. It is important to distinguish allergic reactions to wheat from celiac disease or food intolerance associated with eating wheat products.
Reactions to other foods
Allergic reactions to the above food groups are the most common.
Nevertheless, reactions to a diverse range of food and plant-derived
products such as spices, vegetable gums, herbal
remedies (e.g. Royal Jelly, Echinacea), fruit and vegetables
have been described.
Oral Allergy Syndrome
About 1 in 10 people with allergy to
some grass or tree pollens (hay fever
or seasonal asthma) will complain that some uncooked vegetables
or fresh fruits will make their mouth and throat itchy or swell.
This is known as Oral Allergy Syndrome. In this condition,
people are allergic to proteins that are present in pollens as
well as these foods. If the food is heated, the protein is
destroyed. This is why they can usually eat the cooked food
without a problem. More serious allergic reactions sometimes occur,
particularly if exercise is undertaken soon after eating. People
who are very allergic to multiple fruit and vegetables may suffer
nutritional problems if they have to restrict their diet and heavily
cook their foods. Vitamin supplements and review by a dietitian
may be required.
Allergic reactions to inhaled food
Allergic reactions to food in the form
of fine dust are uncommon, and mainly occur in food handlers.
Examples include asthma induced by the fine dust of coffee or
soy beans in processing plants, seafood allergens in some factories
or wheat dust in bakeries.
