Allergic reactions are sensitivities to substances called allergens
that come into contact with the skin, nose, eyes, respiratory
tract, and gastrointestinal tract. They can be breathed into the
lungs, swallowed, or injected.
In an allergic reaction, the immune system starts fighting
substances that are usually harmless as though these
substances were trying to attack the body.
Many allergic reactions are mild, while others can be severe and
life-threatening and the manifestation that happen according to
the severity of the reaction.
An allergic reaction is more serious when severe allergic
reaction (anaphylaxis) occurs
Types of hypersensitivity (
Allergic Reaction )
Gel and Coombs classification of hypersensitivities.
Anaphylaxis is a sudden,
severe allergic reaction
that can be life-threatening.
It is a medical emergency
It can occur within seconds
or minutes of exposure to
something someone is
Anaphylaxis is under
hypersensitivity type 1
Our immune system produces antibodies that defend against foreign
This is good when a foreign substance is harmful (such as certain
bacteria or viruses).
But some people's immune systems overreact to substances that
shouldn't cause an allergic reaction.
When this occurs, the immune system sets off a chemical chain
reaction, leading to allergy symptoms.
Normally, allergy symptoms are not life-threatening.
But some people have a severe allergic reaction that can lead to
Anaphylaxis can occur in response to almost any foreign substance
The most common causes of anaphylactic shock are:
1. Certain medications, especially penicillin
2. Foods, such as peanuts, tree nuts
(walnuts, pecans), fish, shellfish, milk and eggs
3. Insect stings from bees, yellow jackets, wasps, hornets and fire ants
Less common causes of anaphylaxis include:
1. Exercise, often after eating certain foods.
Anaphylaxis usually happens within minutes of exposure and almost
always within two hours
Anaphylaxis is a severe allergic
reaction of rapid onset affecting many
It is due to the release of
inflammatory mediators and cytokines
from mast cells and basophils,
typically due to an immunologic
reaction but sometimes non-
There aren't many known risk factors for anaphylaxis,
but some things that may increase your risk include:
1. A personal history of anaphylaxis: If you've
experienced anaphylaxis once, your risk of having this
serious reaction is increased. Future reactions may be
more severe than the first reaction.
2. Allergies or asthma: People who have either
condition are at increased risk of having anaphylaxis.
3. A family history: If you have family members who
have experienced exercised-induced anaphylaxis,
your risk of developing this type of anaphylaxis is
higher than it is for someone without a family history.
Sign & Symptoms
Anaphylaxis symptoms include:
1. Skin reactions, including hives along with
itching, flushed or pale skin (almost always
present with anaphylaxis)
2. A feeling of warmth
3. The sensation of a lump in your throat
4. Constriction of the airways and a swollen
tongue or throat, which can cause wheezing
and trouble breathing
5. A feeling of impending doom
6. A weak and rapid pulse
7. Nausea, vomiting or diarrhea
8. Dizziness or fainting
Heart and circulation:
Dizziness, weakness, fainting, rapid, slow,
or irregular heart rate, or hypotension.
Nausea, vomiting, abdominal cramps, or
Nervous system: Anxiety, confusion, or a
sense of impending doom
Allergy testing is ordered to help in
determining the trigger.
Skin allergy testing (such as patch
testing) is available for certain foods
and venoms. Blood testing for specific
IgE can be useful to confirm
milk, egg, peanut, tree nut and fish
Anaphylaxis is diagnosed based on clinical criteria.
When any one of the following three occurs within minutes/hours
of exposure to an allergen there is a high likelihood of
1. Involvement of the skin or mucosal tissue plus either
respiratory difficulty or hypotension.
2. Two or more of the following symptoms:
a. Involvement of the skin or mucosa b. Respiratory
difficulties c. Low blood pressure d. Gastrointestinal
3. Low blood pressure after exposure to a known allerge.
During an attack, blood tests for
tryptase or histamine (released from
mast cells) might be useful in
diagnosing anaphylaxis due to insect
stings or medications. However these
tests are of limited utility if the cause is
food or and they are not specific for
During an anaphylactic attack, an emergency medical team
may perform cardiopulmonary resuscitation (CPR) if the
patient stops breathing or his heart stops beating. He/she
may be given medications including:
1. Epinephrine (adrenaline) to reduce the body's allergic response.
2. Oxygen, to help compensate for restricted breathing.
3. Intravenous (IV) antihistamines and cortisone to reduce
inflammation of air passages and improve breathing.
4. A beta agonist (such as albuterol) to relieve breathing symptoms.
Complication of Anaphylaxis
Cardiac arrest (no effective heartbeat)
Respiratory arrest (no breathing)
The best way to prevent anaphylaxis
is to avoid substances that cause this
If you're with someone having an allergic reaction with
signs of anaphylaxis:
1. Immediately call your local medical emergency number.
2. Ask the person if he or she is carrying an epinephrine
autoinjector to treat an allergic attack (for
example, EpiPen, Twinject).
3. If the person says he or she needs to use an
autoinjector, ask whether you should help inject the
medication. This is usually done by pressing the
autoinjector against the person's thigh.
4. Have the person lie still on his or her back.
5. Loosen tight clothing and cover the person with a
blanket. Don't give the person anything to drink.
6. If there's vomiting or bleeding from the mouth, turn the
person on his or her side to prevent choking.
7. If there are no signs of breathing, coughing or
movement, begin CPR. Do uninterrupted chest presses
— about 100 every minute — until paramedics arrive.
8. Get emergency treatment even if symptoms start to
improve. After anaphylaxis, it's possible for symptoms to
recur. Monitoring in a hospital setting for several hours is