Allergy refers to an excess sensitivity to substances or
conditions such as food; hair; cloth; biological, chemical,
or mechanical agents; emotional excitement; extremes of
temperature; and so on. The hypersensitivity and abnormal reactions associated with allergies produce various
symptoms in affected people. The substance that triggers an allergic reaction is called an allergen or antigen,
and it may enter the body through ingestion, injection,
respiration, or physical contact.
In food allergies, the offending substance is usually,
though not always, a protein. After digestion, it is absorbed into the circulatory system, where it encounters
the body’s immunological system. If this is the first exposure to the antigen, there are no overt clinical signs.
Instead, the presence of an allergen causes the body to
form immunoglobulins (Ig): IgA, IgE, IgG, and IgM. The
organs, tissues, and blood of all healthy people contain
antibodies that either circulate or remain attached to the
cells where they are formed. When the body encounters
the antigen a second time, the specific antibody will complex with it. Because the resulting complexes may or may
not elicit clinical manifestations, merely identifying a
specific immunoglobulin in the circulatory system will
not indicate whether a person is allergic to a specific food
antigen.
The human intestine is coated by the antibody IgA,
which protects a person from developing a food allergy.
However, infants under 7 months old have a lower
amount of intestinal IgA. The mucosa thus permits incompletely digested protein molecules to enter. These
can then enter the circulation and cause antibodies to
form.
Children can also develop a food allergy called the “delayed allergic reaction” or “hypersensitivity.” The classic
sign of this is the tension-fatigue syndrome. Children
with the syndrome have a dull face, pallor, infraorbital
circles, and nasal stuffiness. A delayed food-allergy symptom is more difficult to diagnose than an immediate one.
Although food allergy is not age specific, it is more
prevalent during childhood. Because a reaction to food
can impose stress and interfere with nutrient ingestion,
absorption, and digestion, the growth and development
of children with food allergies can be delayed. Half of the
adult patients with food allergy claim that they had a
childhood allergy as well. Apparently, a childhood food allergy rarely disappears completely in an adult. If a newborn baby develops hypersensitivity in the first five to
eight days of life, the pregnant mother was probably eating a large quantity of potentially offending foods, such
as milk, eggs, chocolate, or wheat. The child becomes
sensitized in the womb, and the allergic tendency may either continue into adult life or gradually decrease.
In clinical medicine, it is extremely important to differentiate food allergy from food intolerance. The former relates to the immuno system of the body, while
the latter is the direct result of maldigestion and malabsorption due to a lack of intestinal enzyme(s) or an indirect intestinal reaction because of psychological
maladjustment.
Food Allergy and Children
SYMPTOMS AND MANAGEMENT
About 2%–8% of all Americans have some form of food allergy. The clinical management of food allergy is controversial and has many problems. For instance, a food
allergy is influenced by the amount of allergen consumed, whether the allergen is cooked or raw, and the cumulative effects from successive ingestions of the
allergen. A person with a food allergy also tends to be allergic to one or more of the following: pollen, mold, wool,
cosmetics, dust, and other inhalable items. Because these
substances are so common, they are difficult to avoid.
Other difficulties in allergy management are as
follows:
1. If a person is allergic to a food, even a very small
amount can produce a reaction.
2. Some patients allergic to an item at one time are not
allergic at another.
3. Some patients react to an allergen only when they
are tired, frustrated, or emotionally upset.
4. Although protein is suspected to be the substance
most likely to cause allergy, people can be allergic to
almost any food chemical.
In managing patients with food allergy, there are two
basic objectives. First, the offending substance must be
identified. Patients should then be placed on a monitored
antiallergic diet to assure adequate nutrient intake,especially young patients whose growth and development
may be adversely affected by the allergy.
The clinical reactions of patients allergic to a food vary
from relatively mild ones such as skin rash, itchy eyes, or
headache to more severe ones such as abdominal cramps,
diarrhea, vomiting, and loss of appetite. Other symptoms
include cough, asthma, bronchitis, purpura, urticaria,
dermatitis, and various problems affecting the digestive
tract (vomiting, colic, ulceration of colon, etc.). In children, undernutrition and arrested development may
occur.
MILK ALLERGY
Many individuals of all ages develop an allergy as well as
an intolerance to milk and milk products. The reaction
may occur when a person is sick (e.g., with infection, alcoholism, surgery, or trauma); thus, dietitians and nurses
should always check to see whether a patient can tolerate milk. If the intolerance is due to a reduced activity of
lactase, proper dietary therapy can be implemented.
Someone allergic to milk must also avoid many foods
containing milk products. Ingesting regular homogenized fresh milk can damage the digestive mucosa of
some susceptible individuals, especially children. The
damaged cells bleed continuously but only minute
amounts of blood are lost. The result is occult blood loss
in the stool and iron-deficiency anemia. Professionals do
not agree about whether this phenomenon is an allergic
reaction. In rare cases, penicillin used in cows to prevent
or control mastitis may leave a residue in milk.
Consequently, some individuals who are allergic to the
penicillin may have an allergic reaction to the inoculated
cow’s milk.
Breastmilk is much preferred over cow’s milk for feeding a baby in a family whose members have allergies.
Cow’s milk contains the protein beta-lactoglobulin,
which may trigger an allergic reaction, while breastmilk
does not. If an infant has symptoms of milk allergy, special formulas with soy or another protein source as a base
can be safely substituted for milk.
However, breastfeeding does have one major problem
when it is used to prevent an infant from having an allergic reaction to cow’s milk. If the child is also allergic to
substances such as cheese, crab, or chocolate, the mother
can in effect feed them to her child via breastmilk if she
ingests them herself. Therefore, the breastfed child may
show allergic reactions.
DIAGNOSIS AND TREATMENT
Food allergies are difficult to test for and subsequently to
diagnose and confirm. Furthermore, patients with an allergic reaction to one food may in reality be allergic to
many others that contain a common ingredient. Or, when
an infant is allergic to a formula, it is usually assumed
that the protein is responsible. In reality, it could be the
vegetable oil base.
When food allergy is suspected in a child, the parents,
nurse, and dietitian or nutritionist should work together
to identify the culprit. The child’s reactions to food coloring and additives (which are found in many processed
foods) and salicylate-related chemicals should also be
noted. Unless the culprit is one of the common offenders,
it is difficult for the physician to make an accurate diagnosis because of the many different components in a
child’s diet.
The National Institute of Health and the Department
of Health and Human Services has made the following
recommendations about diagnosis of a food allergy.
After ruling out food intolerances and other health
problems, your healthcare provider will use several steps
to find out if you have an allergy to specific foods.
Diet Diary
Sometimes your healthcare provider can’t make a diagnosis solely on the basis of your history. In that case, you
may be asked to record what you eat and whether you
have a reaction. This diet diary gives more detail from
which you and your provider can see if there is a consistent pattern in your reactions.
Elimination Diet
The next step some healthcare providers use is an elimination diet. In this step, which is done under your
provider’s direction, certain foods are removed from your
diet. You don’t eat a food suspected of causing the allergy, such as eggs. You then substitute another food-in
the case of eggs, another source of protein.
Your provider can almost always make a diagnosis if
the symptoms go away after you remove the food from
your diet. The diagnosis is confirmed if you then eat the
food and the symptoms come back. You should do this only when the reactions are not significant and only
under healthcare provider direction.
Your provider can’t use this technique, however, if
your reactions are severe or don’t happen often. If you
have a severe reaction, you should not eat the food again.
Skin Test
If your history, diet diary, or elimination diet suggests a
specific food allergy is likely, your healthcare provider
will then use either the scratch or the prick skin test to
confirm the diagnosis.
During a scratch skin test, your healthcare provider
will place an extract of the food on the skin of your lower
arm. Your provider will then scratch this portion of your
skin with a needle and look for swelling or redness, which
would be a sign of a local allergic reaction.
A prick skin test is done by putting a needle just below
the surface of your skin of the lower arm. Then, a tiny
amount of food extract is placed under the skin.
If the scratch or prick test is positive, it means that
there is IgE on the skin’s mast cells that is specific to the
food being tested. Skin tests are rapid, simple, and relatively safe. You can have a positive skin test to a food allergen, however, without having an allergic reaction to
that food. A healthcare provider diagnoses a food allergy
only when someone has a positive skin test to a specific
allergen and when the history of reactions suggests an allergy to the same food.
Blood Test
Your healthcare provider can make a diagnosis by doing
a blood test as well. Indeed, if you are extremely allergic
and have severe anaphylactic reactions, your provider
can’t use skin testing because causing an allergic reaction
to the skin test could be dangerous. Skin testing also
can’t be done if you have eczema over a large portion of
your body.
Your healthcare provider may use blood tests such as
the RAST (radioallergosorbent test) and newer ones such
as the CAP-RAST. Another blood test is called ELISA
(enzyme-linked immunosorbent assay). These blood tests
measure the presence of food-specific IgE in your blood.
The CAP-RAST can measure how much IgE your blood
has to a specific food. As with skin testing, positive tests
do not necessarily mean you have a food allergy.
Double-Blind Oral Food Challenge
The final method healthcare providers use to diagnose food allergy is double-blind oral food challenge.
Your healthcare provider will give you capsules containing individual doses of various foods, some of which
are suspected of starting an allergic reaction. Or your
provider will mask the suspected food within other foods
known not to cause an allergic reaction. You swallow the
capsules one at a time or swallow the masked food and
are watched to see if a reaction occurs.
In a true double-blind test, your healthcare provider
is also “blinded” (the capsules having been made up by
another medical person). In that case your provider does
not know which capsule contains the allergen.
The advantage of such a challenge is that if you react
only to suspected foods and not to other foods tested, it
confirms the diagnosis. You cannot be tested this way if
you have a history of severe allergic reactions.
In addition, this testing is difficult because it takes a
lot of time to perform and many food allergies are difficult to evaluate with this procedure. Consequently, many
healthcare providers do not perform double-blind food
challenges.
This type of testing is most commonly used if a healthcare provider thinks the reaction described is not due to
a specific food and wishes to obtain evidence to support
this. If your provider finds that your reaction is not due
to a specific food, then additional efforts may be used to
find the real cause of the reaction.
NURSING IMPLICATIONS
The nurse should be aware of the following principles
when caring for children with allergies:
1. Diet therapy is used to identify allergic reactions and
also to avoid these reactions.
2. Newborns of parents with allergies should be protected from potential allergens in breastmilk.
3. Breastmilk is the best food for a potentially allergic
infant.
4. Pregnant women with a family history of allergies
should avoid foods known to be allergens to reduce
the risk of sensitizing the infant.
5. Solid foods should be introduced one at a time and
evaluated over several days before adding another.
6. Delay introduction of solid foods in an infant’s diet
to reduce absorption of potential allergens in an immature GI tract.
7. Appropriate substitutions or supplementation of an
allergic child’s diet is essential to prevent malnutrition created by gaps in permitted foods.
8. Children who are allergic to eggs should never be
immunized with vaccines grown on chick embryo.
9. Diabetic children allergic to pork are unable to use
insulin made from hog pancreas.
10. Children with allergens should wear medical alert
tags.
11. Allergens are usually (though not always) proteins.
12. Raw foods are more likely to be allergens than
cooked ones.
13. Parents and children should read all labels carefully
and be taught to look for hidden sources of the
allergen.
14. Foods that cause immediate allergic reactions in susceptible individuals are eggs, seafood, nuts (especially peanuts), and berries.
15. Foods that cause delayed reactions are wheat, milk,
legumes, corn, white potatoes, chocolate, and oranges (citrus).
16. Patients who are allergic to a specific food will react
to other foods in the same family.
17. Foods that cause allergic responses may be reintroduced at a later time because children tend to outgrow food allergies.
18. Differentiate between food allergies and food intolerance. The treatments are very different.
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