Patient Guide & Frequently Asked Questions
Anaphylaxis or anaphylactic shock is the most severe allergic reaction. It
is a massive allergic response affecting the whole body. Anaphylactic shock occurs
when a large number of the bodys mast cells (part of the bodys defense
system) discharge their mediators e.g. histamine, at once. This reaction may involve
any body system; however the skin, nose, throat, lungs, stomach, intestinal tract,
heart, and blood vessels are primarily affected. The first sign of anaphylaxis may
be a red, itchy rash and a feeling of warmth. These may be followed or accompanied
by light-headedness, shortness of breath, or sneezing; a feeling of anxiety; stomach
or uterine cramps; and/or vomiting and diarrhea. In most cases of anaphylaxis the
symptoms are reversed by adrenaline if given early. In other rare cases, the symptoms
are prolonged and may lead to death.
Definition of Anaphylaxis
No universally accepted definition exists because anaphylaxis comprises a constellation
of features. A good working definition is that it involves one or both of two severe
features: respiratory difficulty (which may be due to laryngeal oedema or asthma)
and hypotension (which may present as fainting, collapse, or loss of consciousness).
The confusion arises because systemic allergic reactions can be mild, moderate or
severe. For example, generalized urticaria, angioedema, and rhinitis would not be
described as anaphylaxis, as neither respiratory difficulty nor hypotension
the potentially life threatening features is present.
How does it happen?
One of the effects of mast cell mediators such as histamine is to make blood vessels
wider and more leaky. This effect is beneficial during local infections, when it
occurs in a restricted area of the body, but during anaphylactic shock it occurs
throughout the body. With the same amount of blood coursing through a greatly enlarged
set of channels, there is far less blood available to fill the vessels and the blood
pressure falls to a dangerously low level. This is the cause of the light-headedness.
Often the patient pulse becomes very weak.
Anyone suffering from anaphylactic shock is seriously ill and needs immediate hospital
treatment. There is a very real danger of death if treatment is delayed, especially
if the person is asthmatic, since the airways also become severely narrowed during
Is anaphylaxis always life threatening?
Some anaphylaxis is mild and will go away without treatment. However, since it is
not possible to predict how a reaction will progress, each episode must be taken
Do reactions get worse with successive episodes?
Subsequent reactions could be the same, better or worse. The reason this is so unpredictable
is that the nature of any reaction depends on two main factors: how allergic you
are and the dose of the allergen you are exposed to. While a persons level
of allergy may vary in either direction over time, the dose of allergen is an even
For example, with one reaction you may have eaten 1/100th of a peanut
and with another the equivalent of 3 peanuts. With the 300-fold higher dose your
reaction will almost certainly be much more severe.
The only good research in this area was done with bee sting allergy, in which it
was shown that with subsequent stings (which deliver an approximately equal dose),
reactions were almost always either the same or less severe.
What are the common causes of anaphylaxis?
The most common agents leading to anaphylaxis are drugs, especially
antibiotics like penicillin, foods and
(bees and wasps). Foods that frequently cause anaphylaxis
in allergic persons include - peanuts,
, shellfish, eggs, and seeds. Anaphylactic
reactions have also been reported in persons who have eaten milk,
chocolate, barley, wheat, rice, citrus fruits, melons, bananas, tomatoes, spinach,
mustard, corn, potatoes and soybeans.
More recently, cases of food-related exercise-induced anaphylaxis
have occurred in patients who perform aerobic exercises within several hours of
a meal. It appears that these reactions can be avoided if the meal and exercise
are separated by at least four hours.
Other rare causes of anaphylaxis include: latex
products, blood products, semen and hormones (oestrogen and progesterone).
TREATMENT OF ANAPHYLAXIS
Adrenaline needs to be injected immediately to counteract
the effects of massive histamine release. Anyone at risk of anaphylaxis should carry
a syringe that is pre-loaded with adrenaline. These are made available to anyone
with a strong reaction to bee or wasp stings, or to those with severe
food allergy. Even a relatively mild reaction, such as localized hives in response
to contact with a food, can be the foretaste of something much more serious, and
it is vital that such warnings are heeded.
For those who have had a severe anaphylactic reaction to food in the past, it is
advisable to carry an adrenaline syringe, in case the food is inadvertently eaten
again. There are two adrenaline injection devices on the market in New Zealand,
at present. The Epi-Pen autoinjector comes in an adult and paediatric
dose. Its main advantage is its spring-activated, concealed needle, which is useful
for people who are fearful of needles. The Ana-kit comes in a pre-loaded
syringe with two adult doses per syringe.
It is still necessary to avoid the food, of course the contents of the syringe
will only be effective if a very small amount has been eaten. An aerosol spray containing
adrenaline (Medihaler-Epi) can be issued to those who have suffered
severe swelling of the throat in the past, in case they unintentionally eat the
food again. It may also be useful if you feel you could not cope with giving yourself
an injection in an emergency. The Medihaler-Epi is no longer available in many countries.
Your doctor should be able to prescribe either the injection or the spray.
in using the syringe or the spray if you begin to experience
a severe reaction to food. In this situation a wait-and-see attitude
could be disastrous. The sooner you use the adrenaline, the more effective it will
be, and you will avoid the possibility of lasting, irreversible damage to the body.
Having used the syringe or spray, dial 111 and go to a hospital
or emergency clinic, because you will probably need further treatment.
The adrenaline injection should be repeated every 10 15 minutes until you
are fully recovered. Tell the doctor if you have been taking steroids (e.g. prednisone)
as these may suppress your body's normal ability to produce its own corticosteroids,
which are needed in this crisis situation.
Not all anaphylactic reactions come on immediately. They can sometimes take an hour
or even two hours to develop. There are usually some initial signs that things are
amiss, such as itching or swelling in the mouth, nausea and stomach pains. If the
food is affecting the throat, hoarseness or a lump in the throat sensation
may be the first signs. Should these be followed by more generalized feelings, such
as itching all over, sneezing, runny nose, diarrhea and weakness, a serious anaphylactic
reaction may be developing. Other kinds of sensation that may accompany this stage
are a feeling of warmth, and a peculiar sense of dread or apprehension. Incontinence,
disorientation and abdominal pains may also be experienced. If there are any signs
such as these, do not delay in getting medical help. Go to the
accident and emergency department if you can, and make sure you are seen quickly
– dont sit quietly waiting your turn.
What should be done after the first anaphylactic reaction?
Blood might need to be taken within 1 – 5 hours to measure
Mast cell Tryptase
, if diagnosis is in doubt.
- Refer to an allergy clinic to determine the cause – to prevent future attacks
- Organize self treatment of future reactions (by Allergist or Aware Physician)
Anyone who has had a severe reaction in the past should consider wearing a Medic Alert bracelet with
the relevant information on it. (You can find out how to obtain these bracelets
from your doctor). If you were to eat your culprit food by mistake, or were stung
by the insect you are allergic to, while away from home, and were found unconscious,
it could save your life. Without it, you might not get the correct medical help.
Frequently Asked Questions About Anaphylaxis Treatment
(Adapted & modified from FAN, Robert Wood, MD)
Can any medication be used to prevent Anaphylaxis?
Unfortunately, no medication will reliably prevent anaphylaxis. Some patients take
antihistamines before going out to a restaurant, but this should not be recommended,
as it will not prevent a severe episode.
Do I always need Adrenaline?
This has to be decided on an individual basis in conjunction with your doctor. Patients
with a history of severe reactions should certainly take adrenaline as soon as they
suspect they have eaten a problem food or feel a reaction starting.
In patients with asthma adrenaline should be used more routinely because these patients
are at higher risk for more dangerous reactions.
For patients with a history of milder reactions, such as isolated hives, just giving
an antihistamine and observing them for evidence of more severe reaction may be
Which medicine should be given first?
If you belong to the group of those who have severe reactions, adrenaline should
be given first. If you dont fit into that group, start with antihistamine
and be ready with the adrenaline in case the reaction progresses.
The effects of steroids are not seen for several hours, so immediate administration
is less critical.
Are steroids always needed?
Steroids are usually recommended for any severe reaction, as they might prevent
symptoms from persisting or recurring (biphasic reactions).
Which patients should carry Adrenaline?
This should always be decided on an individual basis after discussion with your
All patients with peanut and nut allergy should carry adrenaline. Many patients
with eggs and milk allergy do not need to carry adrenaline because their reactions
have always been mild.
Once adrenaline is prescribed, it must be carried all the time.
At what age should a child be switched from EpiPen Jr to a full strength EpiPen?
The answer depends on size and not age. The regular strength EpiPen is appropriate
for children over 30Kg. A study published in JACI, Feb 2001 concluded "In young
children at risk for anaphylaxis who weigh 15-30 Kg, adrenaline injected using the
EpiPen Jr appears to have a better benefit-to-risk ratio than the EpiPen.
At what age can a child carry his/her EpiPen?
Probably after the age of 12 might be reasonable. The problem is not knowing how
to inject, but when to inject.
How many doses of adrenaline can be given during an anaphylactic reaction?
Although a single dose is enough in most cases, some cases require multiple doses.
This is the reason why all patients should be taken to an emergency clinic after
administering their first dose of adrenaline.
It is normally recommended that additional doses be given every 10 to 15 minutes
if symptoms persists or worsen
Is Adrenaline harmful or dangerous?
The majority of people who die from anaphylaxis, die because adrenaline was not
given early enough or not enough given. Therefore, we recommend when in doubt give
the adrenaline. The autoinjectors given to patients usually give intramuscular injections
which is adequate for treating anaphylaxis outside the hospital setting, and avoid
the possibility of adrenaline overdose which can occur with giving intravascular
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