Food allergy occurs in about 6% to 8% of children. The majority of food allergic
reactions occur in the first years of a child’s life. As children grow older,
they loose their sensitivity to milk and eggs, but not to peanuts, fish, tree
nuts, and shellfish.
For a child with a food allergy, eating even a tiny amount of a particular food
can cause symptoms such as nausea, skin rash, vomiting, diarrhea, and cramping.
A severe allergic reaction can cause swelling in the throat or mouth, wheezing,
a sudden drop in blood pressure, and severe difficulty breathing. This kind of
severe reaction is called anaphylaxis. Food allergies are the leading cause of
anaphylaxis. Food related anaphylaxis causes 200 deaths per year in the United
WHAT IS FOOD ALLERGY?
Food allergy is an immunologic reaction which results from eating a
particular food or food additive. Food allergy occurs when the body’s
immune system reacts to certain proteins in a particular food.
Food allergy is a reaction that usually involves the IgE (immunoglobulin
WHAT FOODS ARE ASSOCIATED WITH ALLERGIES?
Only a few foods account for 90% of allergic reactions in children. These
foods include: peanuts, milk, eggs, wheat, tree nuts, fish, and shellfish.
Allergies to peanuts and tree nuts account for most fatal anaphylactic
WHAT TYPES OF FOOD ALLERGIES ARE THERE?
Basically, there are IgE-mediated food allergies, non-IgE-mediated food
allergies, and mixed allergies.
(1) IgE-mediated allergies involve the Type I immune mechanism. Examples
Oral allergy syndrome (IgE):
Commonly associated with eating fresh fruits and vegetables.
Symptoms: itching of the mouth, swelling (angioedema) of the tongue, lips,
Immediate gastrointestinal hypersensitivity (IgE):
Often associated with atopic disease, with signs of allergy in other organs.
Symptoms: abdominal pain, nausea, diarrhea, and vomiting.
(2) Non-IgE-mediated allergies involve the Type II immune mechanism.
Dietary protein enterocolitis (Non-IgE):
Protein intolerance in infants – especially to cow’s milk.
Symptoms: recurrent vomiting and diarrhea.
Celiac disease (Non-IgE):
Malabsorption illness, with sensitivity to wheat, rye, and barley.
Symptoms: abdominal pain and chronic diarrhea.
Most adverse food reactions are actually cases of food intolerance. In
fact, only 6% to 8% of children have a true food allergy. Food intolerance
is an abnormal physiologic response to a food or food additive. Food
intolerance is the result of non-immunologic mechanisms.
Food intolerance can be caused by a number of problems, including:
Anatomical problems, metabolic reactions, pharmacologic reactions, toxic
reactions, psychological reactions, infectious reactions, celiac disease,
digestive problems, and reactions to preservatives.
Examples of the various causes of food intolerance follow.
Metabolic reactions: lactase deficiency, favism, pancreatic insufficiency,
galactosemia, and phenylketonuria.
Approximately 2% of infants experience an adverse reaction to milk. Forty
percent of the time, the problem is caused by the body’s deficiency of the
ß-lactase enzyme, a problem also known as lactose intolerance. Lactose
intolerance is not an allergic reaction, however, but a metabolic problem.
The symptoms are: flatulence, abdominal cramps, and diarrhea.
Pharmacologic reactions: histamine, caffeine, tyramine in cheese,
theobromine in chocolate, alcohol, and serotonin in tomatoes.
Flavorings and preservatives: monosodium glutamate, and sodium
Toxic reactions: dyes, seafood toxins, bacterial toxins, fungal toxins,
pesticides, and heavy metal contaminants.
Infectious reactions: Salmonella, Giardia, and hepatitis.
Digestive problems: celiac disease is an enteropathy which leads to
malabsorption of food.
WHAT IS THE MECHANISM OF ALLERGIC REACTION AND ANAPHYLAXIS?
Foods are composed of carbohydrates, proteins, and lipids. The major food
allergens are primarily the water-soluble glycoproteins. In children, the
foods responsible for most of the allergic reactions are:
milk, peanuts, eggs, soybeans, fish, tree nuts, and wheat.
The body’s immune system can overreact to food proteins, called
allergens. An antibody called immunoglobulin E is involved.
An IgE-mediated allergic reaction to food is the result of interactions
involving antigen-presenting cells (APCs), T cells, and B cells.
An antigen (usually a glycoprotein) interacts with an antigen-presenting
Later, T cells are activated, and this causes B lymphocytes to produce IgE
antibodies to the antigen.
The IgE antibodies bind to the IgE receptors of mast cells, macrophages,
basophils, and eosinophils.
When the offending food is eaten again, the food antigen eventually binds
to the complementary IgE on the surface of basophils, mast cells,
eosinophils, and macrophages. At this point, when the IgE antibody meets the
offending food antigen, chemicals are released that act on the throat,
airway, skin, heart, and intestines. These chemicals are: histamine,
leukotrines, prostaglandins, and cytokines. These are the molecules which
are responsible for both mild and severe allergic reactions.
WHAT ARE THE SIGNS AND SYMPTOMS OF FOOD ALLERGY?
A child with a food allergy can have symptoms beginning as soon as 2
minutes after eating the food, or as long as 1 to 2 hours afterwards.
Signs and symptoms of IgE-mediated food allergy can range from very mild
symptoms (oral allergy syndrome) to a severe, life-threatening anaphylactic
reaction. A variety of skin, gastrointestinal, respiratory, and generalized
symptoms are associated with IgE-mediated food allergy.
Examples of food allergy symptoms follow.
Acute urticaria (itching wheals) and angioedema (painful swelling) are the
most common skin manifestations of food hypersensitivity reactions.
The causes in children are usually: milk, peanuts, eggs, and tree nuts.
Oral allergy syndrome:
Localized swelling of the lips, tongue, palate, and throat. Temporary
lingual papillitis (strawberry tongue). These symptoms are usually
well-controlled with an antihistamine, such as Benadryl.
The causes in children are usually: ingestion of a variety of fruits and
Abdominal pain, nausea, abdominal cramping, diarrhea, and vomiting.
Generalized anaphylaxis reaction:
Systemic anaphylaxis is the most severe form of food allergy, and is
The early symptoms of food-induced anaphylaxis often include: tingling in
the throat, oral itching and tingling, shortness of breath, great difficulty
breathing, tightness in the chest, nausea, abdominal pain, vomiting,
swelling of the face, hives, and passing out.
Symptoms usually start within 30 minutes after food ingestion, and rarely 2
hours after ingestion.
Symptoms can sometimes be controlled with prompt intramuscular
administration of adrenaline (epinephrine).
WHAT ARE THE STEPS IN DIAGNOSING A FOOD ALLERGY?
A careful medical history and physical examination of the child are the
most important initial steps in diagnosing a food allergy.
A systematic review of the diet is next:
Patients are often asked to keep a diet diary, which records: foods eaten,
description of symptoms experienced, and the time between ingestion of food
and appearance of symptoms.
Allergy skin prick tests:
Using glycerinated food extracts, a positive control (histamine), and a
negative control (saline), a physician can screen for food allergy.
Unfortunately, the positive predictive accuracy of skin prick tests is only
50%. A negative test result, however, confirms the absence of an IgE-mediated
reaction, and is 95% accurate in excluding a particular IgE-mediated food
Serologic radioallergosorbent test is a blood test which checks for IgE
antibodies against a specific food allergen.
A 1-2-week elimination diet of all foods which are suspected by the
medical history , skin prick tests, or other tests.
Finally, the double-blind, placebo-controlled food challenge is the
“gold standard” for the diagnosis of a food allergy.
WHEN TO GO TO THE HOSPITAL:
An anaphylactic reaction can be life-threatening. Any food reaction that
causes shortness of breath, a feeling of choking, dizziness, or passing out
requires immediate evaluation and treatment in a medical emergency
If a child has shortness of breath, dizziness, tightness in the chest –
then emergency treatment needs to be started.
The hospital treatment will include: adrenaline injection, oxygen
administration, steroid administration, and other medications to relieve the
EMERGENCY MEDICAL TREATMENT FOR SEVERE ALLERGIC REACTION:
Around 200 people die each year in the United States because of
food-related allergic reactions. What follows are the medical steps needed
1) Assess the severity of the allergic reaction.
2) Monitor the patient. Assess the airway, breathing, and circulation.
3) Administer supplemental oxygen by mask, and keep the airway open.
4) Treat severe systemic symptoms with an intramuscular injection of
epinephrine 1:1,000 at 0.01 ml/kg. This can be repeated every 15 minutes, as
5) Administer intravenous fluids to ensure tissue perfusion – 30 ml/kg
6) Treat bronchospasm with albuterol 0.5% at 2 puffs, from a metered-dose
7) Administer an oral or intramuscular antihistamine (Benadryl) at 1
mg/kg, up to a maximum of 75 mg.
8) Administer a systemic corticosteroid such as methylprednisolone, at 2
9) Treat severe reactions with intubation and other advanced lifesaving
techniques, as needed.
WHAT IS THE LONG-TERM TREATMENT FOR FOOD ALLERGY?
Treatment of food allergy consists of: teaching the patient and family how
to avoid the offending food. The family is also taught how to recognize and
manage the symptoms of an allergic reaction.
For management of oral lesions caused by a mild food allergy, the
palliative treatment consists of swabbing a 1:1 mixture of a Benadryl and
Kaopectate on the tongue, lips, and inside of the mouth.
HOW CAN FOOD ALLERGY BE PREVENTED?
The only sure way to prevent food allergies is to avoid eating the foods
which cause the problem.
In restaurants, parents need to ask what ingredients are in the food being
Parents need to carefully read the ingredients on food labels.
A physician will provide the parent with a self-injectable device (Epi-Pen
Jr.) which contains epinephrine for use in a pediatric emergency. Parents
should receive instructions for using this device before leaving the
Children who are a risk for anaphylaxis should wear a medical alert ID
bracelet. This bracelet can alert teachers and medical personnel about the
risk for an allergic reaction.
It is now known that food ingested by a mother can be passed on to the
unborn baby via the uterus, or to the infant via breast milk. Mothers in
high-risk families should consider eliminating peanuts and tree nuts from
their diet during pregnancy and during breastfeeding.
An article in Contemporary Pediatric provides a practical guide
to the diagnosis of food hypersensitivity reactions. It distinguishes
between food allergy and food intolerance. The article describes various IgE-mediated
and non-IgE-mediated food reactions. An overview of the diagnostic approach
to food allergies is also presented.