Pediatric
Food Allergies and Food Intolerance
What
is an Allergy?
An allergy is a hypersensitivity to environmental substances
such as dust, pollen, and certain foods. Allergic individuals
experience adverse reactions that do not normally occur
in a larger population exposed to similar amounts of
the specific allergen. Allergic reactions can be either
local or systematic inflammatory responses.
Local symptoms of an allergic reaction can include swelling
of the nasal mucosa in the nose; redness and itching
of the conjunctiva in the eyes; sneezing, wheezing,
and difficulty breathing in the airways (including asthma
attacks); fullness, pain, and impaired hearing (due
to blockage of Eustachian tubes) in the ears; rashes,
such as eczema, hives, and contact dermatitis, on the
skin; and headaches from sinus pressure.
Systemic responses, or anaphylaxis, can affect multiple
body systems, especially the respiratory, circulatory,
and digestive systems. Severity is variable and extreme
reactions may require injection of epinephrine. Anaphylaxis
can appear to subside and then recur over a prolonged
period of time.
There has been an apparent recent increase in the incidence
of allergies of all kinds. Explanations include improved
diagnosis, extensive use and distribution of chemicals
in all aspects of modern life (multiple chemical sensitivity),
imperfect distinctions between allergies, intolerance,
and actual toxins, and the increased use of antibiotics
and vaccinations in the treatment and prevention of
diseases that may have unintended consequences for the
human immune response.
Food Allergies
A food allergy is an immune system response to diet.
The body mistakes an ingredient in food as harmful and
mounts a defense against it in the form of antibodies.
Allergy symptoms develop as the antibodies battle the
invading food. Common food allergies include peanuts,
tree nuts, fish, shellfish, milk, eggs, soy, and wheat,
affecting as many as 8% of children and 4% of adults.
Food allergies typically develop from a sensitivity
to certain proteins. The first time a food containing
a culprit protein is ingested, the immune system responds
by creating specific antibodies (immunoglobulin E, or
IgE). After sensitization, whenever the food containing
the protein is eaten, IgE antibodies and other chemicals,
including histamine, are released in an attempt to expel
the invader. Histamine is a powerful chemical that can
affect several body systems, not just the gastrointestinal
tract. The amount of food necessary to trigger an allergic
reaction varies among individuals.
Specific symptoms of a food allergy in an individual
depend on where the histamine is released in the body.
Reactions sometimes present a combination or sequence
of symptoms as the food is eaten and proceeds through
the digestive system.
Symptoms of food allergy can range from mild to severe,
and may include:
- Nausea
- Stomach
pain
-
Diarrhea
-
Rash, hives, or itchy skin
-
Shortness of breath
-
Chest pain
-
Swelling of the airways
-
Anaphylaxis
Both children and adults are susceptible to food allergies.
Food allergies often run in families, and while there
is strong evidence that genetic predispositions exist,
they do not tend to fall into simple (classic Mendelian)
inheritance patterns. Both allergies and asthma are
complex genetic disorders involving interactions of
multiple genes, some contributing to disease development
and some having actual protective value, with each gene
having its own variable tendency for expression. Possible
risk factors and protective factors related to environment
and lifestyle have also been suggested by research.
Food Intolerance
Food intolerance is a digestive system response rather
than an immune system response. Something in a food
irritates the digestive system or the system is unable
to properly digest or breakdown the food. As with allergies,
the amount of food necessary to trigger symptoms of
intolerance also varies among individuals.
Symptoms of food intolerance can also range from mild
to severe, and may include:
- Nausea
-
Stomach pain
-
Diarrhea
-
Gas, cramps, or bloating
-
Vomiting
-
Heartburn and reflux
-
Headache
-
Irritability or nervousness
Food intolerance may result from a lack of the specific
enzymes required to properly digest certain proteins,
as in lactose intolerance. Intolerance in some individuals
may also be a reaction to other chemical ingredients
in food, such as additives to provide color, enhance
taste, or protect against bacteria. Sulfites, both naturally
occurring or added to prevent mold, are a source of
intolerance for some individuals. Salicylates, a group
of chemicals found naturally in fruits, vegetables,
nuts, and juices, may be a source of intolerance, triggering
symptoms in individuals who are also sensitive to aspirin.
It is important to note that ANY food consumed in excessive
quantities may cause digestive symptoms indistinguishable
from intolerance.
Allergies,
Intolerance, and Food Refusal
If a child continues to ingest food to which they have
an undiagnosed allergy, even without the more obvious
symptoms or problems with nutrition, lesions or irritations
can form in the digestive track, making eating a painful
ordeal and establishing more general habits of refusal.
Unidentified food intolerances can also result in acute
or chronic problems with digestion and nutrition, that
may or may not be complicated or masked by habits of
refusal.
Diagnosis and Testing
Some pediatric food allergies can remain undiagnosed
for many months, causing worry for parents and health
risks for children and infants. Blood or mucous in the
stool, reflux, skin rashes, and other disturbing symptoms
can be diagnosed as viruses or colic but turn out to
be milk or soy allergies. Identifying ultimate medical
conditions impacting the treatment of eating disorders
requires detailed analysis of possible irritants or
allergens and coincident or subsequent adverse reactions,
even it they are not initially suspected.
Testing for allergies is typically constrained by age-related
patterns of sensitization. Sensitization to foods can
occur in babies only a few weeks old, while it unusual
to develop sensitization to respiratory allergens before
two or three years of age. In preschoolers, sensitization
to indoor allergens (such as pets, dust, or mites) is
more common than sensitization to outdoor allergens
(such as pollen).
If
a pediatric food allergy is suspected a pediatrician
or allergist will review the history and symptoms noted
after ingestion, and if the reactions are consistent
with a food allergy, will order or perform appropriate
tests, of which there are several types:
Skin tests are simple and direct, with results available
in minutes:
Prick Tests: A small amount of suspected
allergen, or a battery of allergens in specifically
labeled locations, is inserted under the skin. A hive,
or redness and swelling will form where there is a reaction
to the specific allergen, and is generally a quick positive
or negative result for IgE.
Patch Tests: The suspected irritant
is applied to the skin topically and held in place with
an adhesive patch. A sterile control patch is also applied
in another location. If a hive, or redness and swelling
appears under the suspect patch but not under the control
patch, then the test is positive.
A skin test cannot predict what kind of reaction might
occur upon ingestion of a food containing the allergen,
but it can confirm an allergy suggested by the patient’s
history of reactions to particular food.
Blood Tests, most commonly radioallergosorbent
test (RAST), can measure the actual amount of IgE antibodies,
which are then compared to predictive values for certain
foods. Blood tests allow for hundreds of allergens to
be screened from a single sample, and cover inhalants
as well as food allergies. However, non-IgE mediated
allergies cannot be detected by this method, There is
some dispute about the significance of blood tests for
Immunoglobulin G (IgG) antibodies, which may be implicated
in delayed-onset food allergies (associated with viruses,
bacteria, and fungi), in contrast to the more common
rapid onset of IgE allergies.
Skin tests may be quicker and more sensitive than blood
tests, depending on technique, but blood tests are less
likely than skin tests to be affected by certain medications
or a preexisting rash. Blood tests are preferred when
the subject may have such a high sensitivity level that
administration of a suspected allergen could have serious
side effects.
Food Challenge Tests are administered
under strict supervision in closely monitored environments,
ideally as double-blind, placebo-controlled tests, in
order to eliminate other factors such as food preparation
techniques or psychological reactions to food recognition.
Elimination Diet is the deliberate
removal of specific suspect foods or ingredients from
a child’s diet. If the symptoms clear up after
a period of time, the pediatrician or allergist will
direct a gradual reintroduction of the avoided foods
or ingredients, one at a time. If symptoms return, a
specific diagnosis can usually be confirmed. This can
be repeated to narrow the range of culprit ingredients.
A dietician can assist in planning menus to compensate
for the absence of nutrients normally found in the potential
allergenic food(s).
Elimination
diets and food challenge tests cannot be used if anaphylactic
or other severe reactions are involved.
Other tests to determine severity and
extent of malnutrition, malabsorption, and systemic
involvement can include:
- Complete
blood count (CBC) to look for anemia
-
Erythrocyte sedimentation rate (ESR) and C-reactive
protein (CRP) to evaluate inflammation
-
Comprehensive metabolic panel (CMP) to determine electrolyte,
protein, and calcium levels
-
Vitamin D, E, and B12 to measure vitamin deficiencies
-
Stool fat to evaluate malabsorption.
Other tools for diagnosis of gastrointestinal
food hypersensitivity and more serious specific disease
conditions include biopsy from upper endoscopy or lower
endoscopy (colonoscopy).
Differential diagnosis is always an important step before
more intrusive measures. Lactose intolerance and celiac
disease are each well known reactions to very specific
proteins. Irritable bowel syndrome may be due to a food
allergy, but is an important diagnosis for intolerance
when no allergens can be identified.
Treatment and Resolution
The primary treatment for food allergies or food intolerance
is avoidance of the foods, or the ingredients in foods,
identified as allergens or as triggers of other adverse
digestive reactions.
About 50% of children with allergies or sensitivities
to milk, egg, soy, or wheat outgrow it by age six or
after. Of those that don’t and are still allergic
by age twelve, less than 8% will eventually outgrow
it. Peanut and tree nut allergies are less likely to
be outgrown. Those children who do outgrow a food allergy
may eventually relapse if they do not consume the former
allergen in some regular fashion.
Risks
Serious risk can be avoided by staying informed and
educating an affected child as they grow and learn to
cope with a food sensitivities, remaining watchful of
diet and environmental triggers, and regularly consulting
a pediatrician about the specific risks associated with
a known food sensitivity. Modest precautions will normally
suffice.
Even airborne food particles can trigger an allergic
reaction. Somewhat like secondhand smoke, there may
be harmful effects for people who aren't directly ingesting
it. Unlike secondhand smoke, which can hurt everybody,
airborne food particles are a hazard only for a very
small minority. An estimated 3 percent of elementary-school-age
children and 2 percent of adults have food allergies,
and the number who are radically sensitive are a mere
fraction of even that relatively small population.
Acknowledging the risks posed to people with food allergies,
many countries have instituted laws that require food
products be labeled if they contain any major allergens
or by-products of major allergens. In the United States,
the Food Allergen Labeling and Consumer Protection Act
of 2004 requires the disclosure in clear, plain language.
A Closer Look
Celiac Disease (CD)
Celiac disease, also called gluten sensitive enteropathy
(GSE) in a autoimmune disorder of the small bowel, and
specific form of gluten intolerance or sensitivity.
Symptoms can include chronic diarrhea, malnutrition,
and fatigue, but these may be absent and other associated
symptoms in other organ systems may be observed instead,
such as dermatitis herpetiformis, an extremely itchy
skin irruption.
The disease is caused by a reaction to a certain gluten
proteins (prolamins) found in wheat, barley, and rye.
It occurs in genetically predisposed individuals whose
enzyme tissue transglutaminise modifies the protein,
causing an inflammatory reaction of the immune system.
This damages the villi in the lining of the small intestine
and interferes with the absorption of any nutrients,
not just those in food containing gluten.
Research has suggested that the timing of exposure to
gluten in childhood may be a factor in developing celiac
disease, but the results in infants exposed to wheat,
barley, or rye at various ages are inconclusive. Breastfeeding
until the introduction of gluten-containing grains does
show a reduced risk of developing celiac disease in
infants.
Diagnosing celiac disease starts with blood antibody
tests to measure levels of anti-endomysium and anti-tissue
transglutaminise, but if positive these are only suggestive.
If negative, then celiac disease is not diagnosed. An
endoscopic biopsy of the small intestine to check for
damage to the villi is the only way to confirm celiac
disease.
Only a small percentage of gluten intolerant children
and adults test positive for celiac disease. Non-celiac
gluten sensitivity (NCGS) is much more common, affecting
as many a one in seven. A gluten challenge diet may
be administered months or years after diagnosis of celiac
disease in infants, since features of celiac disease
may be mimicked other conditions such as secondary disaccharidase
deficiency or milk intolerance.
The only known effective treatment for celiac disease
is a life-long gluten-free diet. Strict adherence to
the diet allows the intestines to heal, and in a majority
of individuals leads to the resolution of all symptoms,
although there may be a persistence of related symptoms
suggestive of irritable bowel syndrome.
Food and Asthma
Asthma results when environmental triggers cause swelling
in the air passages and the lungs. Symptoms can include
wheezing, shortness of breath, and coughing, with attacks
normally triggered by particles in the air, or sudden
changes in air temperature. Although food-triggered
asthma is unusual, food allergies can themselves affect
asthma is a variety of ways, and may share the same
symptoms. Food ingredients that may trigger asthma attacks
include: chemical additives such as benzoates, sulphites,
or gallates, and some coloring agents; naturally occurring
yeasts and molds, as in bread or cheese; dairy products,
wheat, eggs, seafood, soy, and nuts.
Some foods can reduce the severity of an asthma attack
by dilating air passages and thinning the mucus, promoting
freer breathing. In this category, spicy or pungent
foods like chili, hot mustard, garlic, and onions work
by stimulating nerves and releasing fluid in the mouth,
throat, and lungs. Some foods, such as onions, fatty
fish (high in omega-3 fatty acids), and others high
in vitamin C also contain anti-inflammatory components
that help clear the airways. Beverages containing caffeine
may also provide relief. Of course, strong spices or
stimulants are not recommended for infants or small
children.
Children are more likely to outgrow asthma if their
blood tests show fewer and fewer allergy markers as
they get older. Only some have asthma that is trigged
by allergies, and only some of those allergies may be
from food. If a child needs daily asthma medication,
it's important for them to take them, but long-term
use of asthma drugs has no effect on outgrowing asthma.
Even using inhaled steroids has no effect on the outgrowing
of asthma. If fact, children are more likely to outgrow
asthma by outgrowing an allergy, if they do not improve
with inhaled steroids. Since inhaled steroids reduce
inflammation and sensitivity to allergy triggers, this
is a sign the asthma may not have been caused by allergies
in the first place.
Lactose Intolerance (LI)
Intolerance to lactose in milk and other dairy products
is common diagnosis in children, and physiologically
normal for most adults. Lactose is the main sugar in
milk, and the only significant sugar from animal origin.
The intestinal enzyme lactase in required to digest
lactose, acting to break the bond between galactose
and glucose. Most humans, like most mammals, tend to
lose the ability to produce lactase after infancy. Significant
production of lactase ceases between the ages of two
and five.
Symptoms of lactose intolerance are caused by enteral
bacteria in the digestive tract metabolizing the relative
abundance of unabsorbed lactose, drawing excess water
into the intestines and producing gas by fermentation
in the colon. This can result in stomach cramps, bloating,
flatulence, and diarrhea.
A common tool for diagnosis is the hydrogen breath test,
checking for evidence of incomplete digestion before
and after ingestion of lactose. Biopsy from upper or
lower endoscopy can test for the presence or absence
of lactase.
Incomplete absorption of lactose in normal infants with
regular feeding patterns is called functional lactase
deficiency, common in the first week of life and persisting
for up to five months. Primary acquired lactase non-persistence
occurs after weaning from breast milk and is very common
up to six years of age. Secondary acquired lactase non-persistence
is the result of damage to the mucosa of the small intestine,
possibly from gastroenteritis or celiac disease. Congenital
alactasia, or hypolactasia, is an extremely rare condition,
found mainly in Scandinavia, in which infants affected
do not gain weight and fail to thrive. Diagnosis must
also distinguish lactose intolerance from milk allergy
(see below).
Milk Allergy
An allergic reaction to one or more proteins in milk
can cause an infant to be fussy and irritable, with
upset stomach and other symptoms. Many children who
are allergic to cow’s milk may also react to goat’s
and sheep’s milk, and some may also be allergic
to protein in soy milk. Infants who are breastfed are
less likely to develop a milk allergy than infants who
are formula fed, but it is not clear why some develop
a milk allergy and others do not. As with many allergies,
there may be a genetic predisposition.
Symptoms of milk allergy usually appear with the first
few months of infancy. A slow-onset reaction is more
common, occurring a week or so after consuming cow’s
milk, and involving loose stools, vomiting, gagging,
food refusal, colic, or rashes. Less common rapid-onset
reactions come on suddenly after feeding, involving
vomiting, wheezing, swelling, or hives. Anaphylaxis
can occur, but this potentially serious reaction is
more common in other food allergies than in a milk allergy
There is no single test to diagnose a milk allergy,
and symptoms can be similar to lactose intolerance and
other health conditions. A pediatrician may order a
skin test in addition to a stool test and blood test.
Repetitive oral challenge tests are sometimes necessary
to confirm a diagnosis.
if breastfeeding, treatment includes restricting dairy
products in the mother’s diet, which should then
be supplemented with alternative sources of calcium
and other nutrients. If formula feeding, a pediatrician
may advise soy-based formula. If soy is also not tolerated,
then hypoallergenic formula may be recommended. Goat’s
milk, rice milk, or almond milk are not recommended
for infants. Once the switch away from milk is made,
symptoms should disappear in a few weeks. Most children
outgrow a milk allergy by age two, but it can persist
into adulthood.
Peanut and Tree Nut Allergies
An allergic reaction or hypersensitivity to a variety
of dietary substances in peanuts can lead to a range
of symptoms in as many as 1% of children and adults.
Symptoms can include frequent urination, hypotension,
hives, flushing, vomiting, itching, and bronchial constriction.
The most severe cases result in anaphylaxis requiring
immediate medical attention and treatment with epinephrine.
As with most allergies, avoidance and dietary exclusion
is the only effective treatment, but around 25% of children
with a peanut allergy grow out of it.
Tree nut allergies are distinct from peanut allergies,
in that they are different foods with different allergenic
components, and a allergy to one does not mean an allergy
to the other, although they can both occur in the same
individual. Symptoms of other nut allergies are very
much the same as those for peanut allergies. Tree nut
allergies do occur mainly in children, may be less common
than peanut allergies, and are usually also treated
by exclusion and avoidance of suspect nuts, nut particles,
and nut oils.
Eosinophilic Esophagitis (EE)
Eosinophilic esophagitis is caused by the infiltration
into the esophagus of a large number of eosinophils,
a type of white blood cell, causing inflammation. Eosinophils
 are
an important part of the immune system, helping resist
certain types of infections, such as parasites. A variety
of stimuli, including certain foods, may trigger abnormal
production and accumulation of eosinophils.
People with EE often have other allergic diseases such
as asthma or eczema. EE can affect people of all ages,
gender and ethnic backgrounds. In some families, there
may be an inherited tendency or genetic predisposition.
EE is thought to be the most common type of eosinophil-associated
gastrointestinal disorder.
The diagnosis of EE is often delayed, sometimes for
years, because of lack of awareness of these disorders
and disagreement concerning specific criteria, but the
diagnosis can be confirmed with biopsies in the majority
of cases. In rare cases, it may be difficult to distinguish
eosinophilic esophagitis from gastroesophageal reflux
disease (GERD).
Most children with EE respond favorably to dietary treatments.
Dietary restrictions can be guided by food allergy testing
and refined by food trials once the symptoms are resolved.
Medications for EE most commonly include steroids to
control inflammation and suppress the eosinophils, if
dietary measures do not resolve the symptoms.
Links
to key .org and .gov sites
American Academy of Allergy, Asthma and Immunology
www.aaaai.org
American Academy of Otolaryngology – Kids ENT
www.entnet.org/KidsENT/Pediatric-Food-Allergies.cfm
Asthma and Allergy Foundation of America
www.aafa.org/
Centers for Disease Control and Prevention
www.cdc.gov/datastatistics/
FDA Center for Food Safety and Applied Nutrition
www.cfsan.fda.gov/~dms/wh-alrgy.html
National Center for Biotechnology Information
www.ncbi.nlm.nih.gov/sites/entrez
National Foundation for Celiac Awareness
www.celiaccentral.org/
National Institutes for Health Clinical Center
ww.clinicalstudies.info.nih.gov/
UCSF Children’s Hospital – Managing Food
Allergies
www.ucsfhealth.org/childrens/edu/foodAllergies.html
USDA Resource List on Food Allergies and Intolerances
www.nal.usda.gov/fnic/pubs/bibs/gen/allergy.htm
Citations
Metcalfe, Dean D., Hugh A. Sampson, and Ronald A. Simon,
eds. 1997. Food Allergy: Adverse Reactions to Foods
and Food Additives. 2nd ed. Cambridge, MA: Blackwell
Science.
Clinical and Immunological Evaluation of Children with
Allergic Disease
www.clinicalstudies.info.nih.gov/detail/A_2005-I-0084.html
Allergies and Intolerance in Children (536 citations)
www.ncbi.nlm.nih.gov/sites/entrez?db=PubMed&cmd
=Search&Term=Allergies
and Intolerance in Children&itool=
QuerySuggestion
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