common Food allergies and intolerances observed

Food allergence and intolerance
Food allergy is an abnormal response to a
food triggered by the body’s immune system.
 food allergy refers to a particular type of
response of the immune system in which the
body produces what is called an allergen, or
IgE, antibody to a food.
(IgE, or immunoglobulin E, is a type of protein
that works against a specific food.)

• Allergic reactions to food can cause serious
illness and, in some cases, death.
• Therefore, food allergy, it is extremely
important to work to find out what food(s)
causes allergic reaction.

• Sometimes, a reaction to food is not an
allergy at all but another type of reaction
called “food intolerance.”
• Food intolerance is more common than food
allergy.
• The immune system does not cause the
symptoms of food intolerance, though these
symptoms may look and feel like those of a
food allergy.

• An immediate allergic reaction involves two
actions of the immune system.
• Immune system produces IgE.,This protein is
called a food-specific antibody, and it circulates
through your blood.
• The food-specific IgE then attaches to mast cells
and basophils.
Basophils are found in blood.
Mast cells are found in body tissues, especially in
areas of body that are typical sites of allergic
reactions. (sites include nose, throat, lungs,
skin, and gastrointestinal (GI) tract.)

• Generally, immune system will form IgE against
a food ( if there is a family history)—not
necessarily food allergies but perhaps other
allergic diseases, such as hay fever or asthma.
• Those who are having two allergic parents,
they are more likely to develop food allergy
than someone with one allergic parent.
• If the immune system is inclined to form IgE to
certain foods, then exposing to the food itself
can have an allergic reaction.

• As this food is digested, it triggers cells in
the body to produce a food-specific IgE in
large amounts.
• The food specific IgE is then released and
attaches to the surfaces of mast cells and
basophils.
The next time when the body is again exposed
to that food, it interacts with food specific
IgE on the surface of the mast cells and
basophils and triggers those cells to release
chemicals such as histamine.

• Depending on the tissue in which they are
released, these chemicals will cause various
symptoms of food allergy.
• Food allergens are proteins in the food that
enter bloodstream after the food is digested.
From there, they go to target organs, such as
skin or nose, and cause allergic reactions.
• An allergic reaction to food can take place
within a few minutes to an hour.
• The process of eating and digesting food
affects the timing and the location of a
reaction.

• If the body is allergic to a particular food, first feel
itching will start in the mouth with the first
contact of the food.
• After the food is digested in your stomach, you
may have GI symptoms such as vomiting,
diarrhea, or pain.
• When the food allergens enter and travel through
your bloodstream, they may cause blood
pressure to drop.
• As the allergens reach skin, they can cause hives
or eczema.
• When the allergens reach mouth and lungs, they
may cause throat tightness and trouble reathing.

Common Food Allergies
• In adults, the foods that most often cause allergic reactions include
• Shellfish such as shrimp, crayfish, lobster, and crab
• Peanuts • Tree nuts such as walnuts
• Fish • Eggs
The most common foods that cause problems in children are
• Eggs • Milk
• Peanuts • Tree nuts
Peanuts and tree nuts are the leading causes of the potentially deadly
food allergy reaction called anaphylaxis.
• Adults usually keep their allergies for life, but children sometimes
outgrow them more likely to outgrow allergies to milk, egg, or soy,
however, than allergies to peanuts.
• The foods to which adults or children usually react are those foods they
eat often.
• For eg:- In Japan, rice allergy is frequent.
• In Scandinavia, codfish allergy is common.

• To find out the difference between food allergy and food intolerance, go
through a list of possible causes for symptoms. This is called a
“differential diagnosis.” This type of diagnosis helps confirm that indeed
have a food allergy rather than a food intolerance or other illness.
• Types of Food Intolerance
• Food poisoning :- One possible cause of symptoms like those of food
allergy is food contaminated with microbes (bacteria, and bacterial
products, such as toxins)
• Contaminated meat and dairy products sometimes cause symptoms,
including GI discomfort, that resemble a food allergy when it is really a
type of food poisoning.
• Histamine toxicity :- There are substances, such as the powerful
chemical histamine, present in certain foods that cause a reaction
similar to an allergic reaction.
Eg:- Histamine can reach high levels in cheese, some wines, and certain
kinds of fish such as tuna and mackerel.
• In fish, histamine is believed to come from contamination by bacteria,
particularly in fish that are not refrigerated properly.
• foods with a high level of histamine, could have a reaction that strongly
resembles an allergic reaction to food. This reaction is called “histamine
toxicity.”

• Lactose intolerance:- Another cause of food intolerance
confused with a food allergy is lactose intolerance or lactase
deficiency. This common food intolerance affects at least 1
out of 10 people.
• Lactase is an enzyme present in the lining of the gut. Lactase
breaks down or digests lactose, a sugar found in milk and
most milk products.
• Lactose intolerance, or lactase deficiency, happens when
there is not enough lactase in the gut to digest lactose.
• In that case, bacteria in gut use lactose to form gas which
causes bloating, abdominal pain, and sometimes diarrhea.
• Food additives :- Another type of food intolerance is a
reaction to certain products that are added to food to
enhance taste, provide color, or protect against the growth of
microbes.
• Several chemical compounds, such as MSG (monosodium
glutamate) and sulfites, are tied to reactions that can be
confused with food allergy.

MSG :- is a flavor enhancer and, when taken in large amounts, can cause
some of the following signs:
• Flushing • Sensations of warmth
• Headache • Chest discomfort
• Feelings of detachment
These passing reactions occur rapidly after eating large amounts of food to
which MSG has been added.
• Sulfites:- Sulfites occur naturally in foods or may be added to increase
crispness or prevent mold growth. In high concentrations sometimes
pose problems for people with severe asthma.
• Sulfites can give off a gas called So2 that a person with asthma inhales
while eating food containing sulfites.
• This gas triggers the nerve endings to constrict (irritates) the lungs and
can send an asthmatic into severe bronchospasm, a tightening of the
lungs.
• The (FDA) has banned sulfites as spray-on preservatives in fresh fruits
and vegetables. Sulfites are still used in some foods, however, and occur
naturally during the fermentation of wine.

• Gluten intolerance:- Gluten intolerance is associated with
the disease called “gluten-sensitive enteropathy” or “celiac
disease.”
• It happens if the immune system responds abnormally to
gluten, which is a part of wheat and some other grains.
• Some researchers include celiac disease as a food allergy.
This abnormal immune system response, however, does not
involve IgE antibody.
• Psychological causes :- Some people may have a food
intolerance that has a psychological trigger.
• If food intolerance is caused by this type of trigger, requires
a careful psychiatric evaluation and treatment.
• Other causes :-There are several other conditions, including
ulcers and cancers of the GI tract, that cause some of the
same symptoms as food allergy.
• These symptoms include vomiting, diarrhea, and cramping
abdominal pain made worse by eating.

Diagnosis
• After ruling out food intolerances and other health problems,
find out the allergy to specific foods.
• Detailed History:- A detailed history is the most valuable tool
for diagnosing food allergy.
Some eg are :-
• What was the timing of the reaction?
• Did the reaction come on quickly, usually within an hour after
eating the food?
• Did allergy medicines help?
Is the reaction always associated with a certain food?
• Did anyone else who ate the same food get sick?
For example:- if the fish contaminated with histamine, everyone
who ate the fish should be sick.
• How much amount had a reaction?
The severity of a reaction is sometimes related to the amount of
food eaten.
• How was the food prepared?

Some people will have a violent allergic reaction
only to raw or undercooked fish. Complete
cooking of the fish may destroy the allergen, and
they can then eat it with no allergic reaction.
• Did other foods at the same time had the
reaction? Some foods may delay digestion and
thus delay the start of the allergic reaction.
• Elimination Diet :-
certain foods are removed from your diet and check
the levels of comfort.

• Skin Test:-
• During a scratch skin test, an extract of the food on
the skin of your lower arm will be placed and then
scratch this portion 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.

• Blood Test :-Blood tests such as the RAST
(radioallergosorbent test) and newer ones
such as the CAP-RAST, ELISA (enzymelinked
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.

• Double-Blind Oral Food Challenge:-
• The advantage of such a challenge is
that .,react only to suspected foods
and not to other foods tested, it
confirms the diagnosis.
• 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.

Treatment
• Food allergy is treated by avoiding the foods
that trigger the reaction. Read the detailed
ingredient lists on each food you are
considering eating.
• Many allergy-producing foods such as
peanuts, eggs, and milk, appear in foods one
normally would not associate them with.
• An auto-injector device containing
epinephrine (adrenaline), such as an epipen or
twinject is used for food allergic reaction

• Seek medical help immediately, if already
given epinephrine, by either calling the
rescue squad or by getting transported to an
emergency room Anaphylactic allergic
reactions can be fatal even when they start
off with mild symptoms such as a tingling in
the mouth and throat or GI discomfort.

• Manage children if they eat a food to which they
are allergic
and adults.
• There are several medicines to relieve food allergy
symptoms that are not part of an anaphylactic
reaction. These include
• Antihistamines to relieve GI symptoms, hives, or
sneezing and a runny nose
• Bronchodilators to relieve asthma symptoms
It is not easy to determine if a reaction to food is
anaphylactic, however, It is important to develop a
plan to what reactions you should treat with
epinephrine first, rather than antihistamines or
bronchodilators.

Food Allergy in Infants and Children
• Allergy to cow’s milk is particularly common in infants and
young children.
• It causes hives and asthma in some children. In others, it
can lead to colic and sleeplessness, and perhaps blood in
the stool or poor growth.
• Infants are thought to be particularly susceptible to this
allergic syndrome because their immune and digestive
systems are immature.
• Milk allergy can develop within days to months of birth.
• There is no conclusive evidence that breast feeding
prevents allergies from developing later in your child’s life.
It does, however, delay the start of food allergies by
delaying your infant’s exposure to those foods that can
prompt allergies.

Some Controversial and Unproven Theories
• There are several disorders that are popularly
thought by some to be caused by food allergies.
• Migraine headaches:-
Studies show people who are prone to migraines can
have their headaches brought on by histamine and
other substances in foods.
• Arthritis:- There is virtually no evidence that most
rheumatoid arthritis or osteoarthritis can be made
worse by foods, despite claims to the contrary.
• Allergic tension fatigue syndrome :- There is no
evidence that food allergies can cause a disorder
called the allergic tension fatigue syndrome, in
which people are tired, nervous, and may have
problems concentrating or have headaches.

• Cerebral allergy:- These symptoms are sometimes blamed on mast
cells activated in the brain but no other place in the body
• Environmental illness :- In a seemingly pristine environment, some
people have many nonspecific complaints such as problems
concentrating or depression.
• Childhood hyperactivity :-Some people believe hyperactivity in
children is caused by food allergies. however,it was found that this
behavioral disorder in children is only occasionally associated with
food additives, and then only when such additives are consumed
in large amounts.
• There is no evidence that a true food allergy can affect a child’s
activity except for the possibility that if a child itches and sneezes
and wheezes a lot, the child may be uncomfortable and therefore
more difficult to guide.
• Also, children who are on anti-allergy medicines that cause
drowsiness may get sleepy in school or at home.

• Cytotoxicity testing :- One controversial diagnostic
technique is cytotoxicity testing, in which a food
allergen is added to a blood sample. A technician
then examines the sample under the microscope to
see if white cells in the blood “die.”
• Provocative challenge:- Another controversial
approach is called sublingual (placed under the
tongue) or subcutaneous (injected under the skin)
provocative challenge.
• In this procedure, diluted food allergen is put under
your tongue if you feel that your arthritis, for
instance, is due to foods. The technician then asks
you if the food allergen has made your arthritis
symptoms worse. In clinical studies, researchers have
not shown that this procedure can effectively
diagnose food allergy.

• Immune complex assay :-An immune complex assay
is sometimes done on people suspected of having
food allergies to see if groups, or complexes, of
certain antibodies connect to the food allergen in
the bloodstream. Some think that these immune
groups link with food allergies..
• IgG subclass assay:- Another test is the IgG subclass
assay, which looks specifically for certain kinds of
IgG antibody
• Allergy shots:- Another unproven treatment
involves getting allergy shots (immunotherapy)
containing small quantities of the food extracts to
which are allergic.

Research
• The National Institute of Allergy and Infectious Diseases
conducts research on food allergy and other allergic diseases.
• This research is focused on understanding what happens to the
body during the allergic process—the sequence of events
leading to the allergic response and the factors responsible for
allergic diseases.
• This understanding will lead to better methods of diagnosing,
preventing, and treating allergic diseases. Researchers also are
looking at better ways to study allergic reactions to foods.
• Educating people, including patients, healthcare providers,
school teachers, and daycare workers, about the importance of
food allergy is also an important research focus.
• The more people know about the disorder, the better
equipped they will be to control food allergies.

• Reference:- Allergy Extracts ;Food and Drug
Administration Center for Biologics Evaluation
and Research 1401 Rockville Pike Rockville,
MD 20852-1448 1–800–835–4709 or 301–
827–1800 www.fda.gov/cber

common Food allergies and intolerances observed

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common Food allergies and intolerances observed