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Anaphylaxis |
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AnaphylaxisMany people experience allergy symptoms which are only a minor annoyance. However, a small number of highly allergic individuals are susceptible to a life-threatening allergic reaction known as anaphylaxis. Anaphylaxis, the most serious type of allergic reaction, is extremely rare. Symptoms usually appear rapidly - within seconds or minutes-after exposure to an allergen (a substance which causes an allergic reaction). In a few cases, however, reactions have been delayed as much as 12 hours. Symptoms of
Anaphylaxis
In anaphylaxis, cells of the immune system release massive amounts of chemicals - particularly histamine. As a result, blood vessels dilate and begin to leak fluid into surrounding tissues, producing swelling. Several organs can be affected:
It's worth repeating that anaphylaxis is rare. The vast majority of people with allergies will never have an anaphylactic reaction. Triggers of
Anaphylaxis
An anaphylactic reaction
is usually triggered by a limited number of allergic exposures. These include
injection, swallowing, inhaling or skin contact with an allergen by a severely
allergic individual. Examples of injected
allergens are bee, hornet, wasp and yellow jacket stings; certain vaccines which
have been prepared on an egg medium; and allergen extracts used for diagnosis
and treatment of allergic conditions. Antibiotics such as penicillin can trigger
a reaction by injection or ingestion (swallowing). Typically, a severe
reaction caused by a food allergy occurs after eating that particular food, even
a small bite. Skin contact with the food
rarely causes anaphylaxis. Foods most commonly associated with anaphylaxis are
peanuts, seafood, nuts and, in children particularly, eggs and cow's milk. An anaphylactic reaction
from an inhaled allergen is rare. An increasingly recognizable example is when
an allergic individual inhales particles from rubber gloves or other latex
products. For some people, two or
more factors may be needed to cause anaphylaxis. Recently, it has been
recognized that some persons have experienced an anaphylactic reaction if they
eat a certain food, and then exercise. Neither the food alone nor exercise alone
causes any problem for these individuals. When exposed to a foreign
substance, some people suffer reactions identical to anaphylaxis, but in which
no allergy is involved. These reactions are called anaphylactoid (meaning
anaphylaxis-like) reactions. While the immune system must be "primed"
by previous exposure to cause anaphylaxis, anaphylactoid reactions can occur
with no previous exposure at all. An example of something that can bring on this
kind of reaction is radiographic contrast material (the dye injected into
arteries and veins to make them show up on an X-ray). Fortunately, health care
providers don't need to distinguish between anaphylactic and anaphylactoid
reactions during an emergency because the treatment is the same. Prevention
of Anaphylaxis
To prevent anaphylaxis, it
is important to avoid the allergen that causes the reaction. That may not be
easy since stinging insects can find their way indoors and allergenic foods can
be concealed in a wide variety of preparations. Precautions can lower the
risk of anaphylaxis and minimize the severity of reactions. For many people,
immunotherapy ("allergy shots") can help. For example, immunotherapy
for bee, wasp, hornet and yellow jacket stings gives effective protection 98% of
the time. There is some risk when an individual with past episodes of
anaphylaxis is injected with an allergen, but experienced health care
professionals working in a controlled setting can make that risk negligible. If immunotherapy is not
practical or available for a particular allergen, the physician has other
options. For example, if someone has experienced an anaphylactic reaction to
penicillin, the physician might order skin tests before giving certain other
types of antibiotics. In most cases, different classes of antibiotics are
available. Individuals who have a history of severe reactions to medications
should take a new medication orally (by mouth) whenever possible, because the
risk of anaphylaxis is higher with an injection. Rarely, someone may get an
infection that requires treatment with an antibiotic known to cause anaphylaxis
in that individual. In this case, rapidly increasing oral (by mouth) doses of
the antibiotic under carefully controlled conditions can often desensitize the
person. Physicians sometimes
suggest that individuals who have had an anaphylactic reaction carry an
epinephrine syringe designed for self-administration. This is particularly
important if the allergen that causes the reaction is difficult to avoid. This
type of medication, available by prescription only, is sold under the name
Ana-Kit®, EpiPen® or EpiPen Jr.® (for children). We recommend that the
patient, and any person who might be in a position to administer the injection,
receive training in the use of these syringes. We also recommend that anyone at
risk for anaphylaxis wear a Medic-Alert® bracelet. Some medicines given for
high blood pressure (called beta blockers) can partially counteract the effects
of epinephrine, making the treatment of anaphylaxis more difficult. Allergic
individuals with high blood pressure may need to ask their physician about
switching to a different type of high blood pressure medication. Treatment
of Anaphylaxis
If you suspect that an
anaphylactic reaction is occurring, immediately seek medical help. Treatment
must begin before blood pressure and breathing problems become life-threatening. Epinephrine is the most
important medication for the treatment of anaphylaxis. It is injected under the
skin or into a muscle. Epinephrine works rapidly to make blood vessels contract,
preventing them from leaking more fluid. It also relaxes airways, helping the
individual breathe easier, relieves cramping in the gastrointestinal tract and
stops itching and hives. Even if the individual
responds to the epinephrine, it is vitally important to go to an emergency room
immediately! Other treatments may be given such as oxygen and medications to
improve breathing. Intravenous fluids may be necessary to restore adequate blood
pressure. Additional medications may be given to counteract the effects of
histamine and to help prevent a delayed allergic reaction. |
Contact
DrNejat@NYAllergy.com with
questions or comments about the content on this web site.
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