Anaphylaxis (Severe Allergic Reaction)

  • Medical Author:
    Jerry R. Balentine, DO, FACEP

    Dr. Balentine received his undergraduate degree from McDaniel College in Westminster, Maryland. He attended medical school at the Philadelphia College of Osteopathic Medicine graduating in1983. He completed his internship at St. Joseph's Hospital in Philadelphia and his Emergency Medicine residency at Lincoln Medical and Mental Health Center in the Bronx, where he served as chief resident.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

View 10 Common Allergy Triggers

Quick Guide10 Common Allergy Causes

10 Common Allergy Causes

What happens after the symptoms begin?

There are three possible outcomes:

  1. The signs and symptoms may be mild and fade spontaneously or be quickly ended by administering emergency medication. In this outcome, the symptoms do not subsequently recur from this particular exposure.
  2. After initial improvement, the symptoms may recur within four to 12 hours (late phase reaction) and require additional treatment and close observation. Recent evidence suggests that a late-phase reaction occurs in fewer than 10% of cases.
  3. Lastly, the reaction may be persistent and more severe, thus requiring intensive medical treatment and hospitalization.

Epinephrine, which is also known as "adrenaline," is a drug that acts immediately to cause the blood vessels to contract, thereby preventing fluid leakage. It is one of the medications frequently used to treat anaphylaxis. Epinephrine also helps relax the bronchial tubes, thus relieving breathing difficulty. It also lessens stomach cramps and stops itching and hives. More importantly, epinephrine helps prevent the release of more mediators of the allergic reaction.

In addition to epinephrine, other medications and IV fluids and oxygen will probably be administered once one receives care from a health-care professional. The choice of interventions will depend on the severity of the reaction the patient experiences. Epinephrine given to someone who does not have anaphylaxis can lead to a dangerously fast heartbeat and severe hypertension. It should only be administered by medical personnel familiar with its use and indications or patients who were prescribed an EpiPen by their health-care provider.

Are there any disorders that appear similar to anaphylaxis?

Several disorders may appear similar to anaphylaxis. Fainting (vasovagal reaction) is the reaction that is most likely to be confused with anaphylaxis. The key differences are that in a fainting episode, the affected person has a slow pulse, cool and pale skin, and no hives or difficulty breathing. Other conditions, such as heart attacks, blood clots to the lungs, septic shock, and panic attacks can also be confused with anaphylaxis.

How is anaphylaxis diagnosed?

If someone thinks he or she is having an anaphylactic reaction, the first order of business is to seek emergency care. Once the acute reaction has been treated, one should follow up with a doctor who will probably recommend seeing an allergist. The allergist will assess whether or not the reaction was indeed allergic in nature. Usually, a careful and detailed medical history and selected blood or skin tests can identify the cause. Be prepared to recall any activities that preceded the event, the food and medications ingested, and whether or not one had any contact with rubber products.

Table 1: The Common Causes of Anaphylaxis

Causes - IgE MediatedExamples
MedicationsPenicillin, cephalosporin, anesthetics, streptokinase, others
Insect stingsHornet, wasp, yellow jacket, honey bee, fire ant
FoodsPeanuts, tree nuts, fish, shellfish, eggs, milk, soy, wheat
VaccinesAllergy shots, egg and gelatin-based vaccines
HormonesInsulin, possibly progesterone
LatexRubber products
Animal/human proteinsHorse serum (used in some snake antivenins)

Causes - Non IgE MediatedExample
MedicationNonsteroidal anti-inflammatories (aspirin, Motrin, etc.), morphine, muscle relaxants (Robaxin, Norflex, and others), gamma globulin
X-ray dye
PhysicalExercise, heat-induced urticaria (hives), cold-induced urticaria
IdiopathicUnknown cause

Two situations deserve special attention at this point since they are not covered elsewhere but are particularly interesting.

  1. In the 1970s, it was noted that exercise could cause anaphylaxis. Exercise-induced anaphylaxis (EIA) usually occurs with prolonged, strenuous exercise. Conditioned athletes such as marathon runners can be affected. The reaction may occur while exercising shortly after eating a meal, after eating specific foods (for example, lettuce, shellfish, or celery), or after taking aspirin. It appears as though food or aspirin loads the gun and exercise pulls the trigger. Early symptoms are usually flushing and itching, which may progress to other typical symptoms of anaphylaxis if the exercise continues. Premedication with antihistamines or other drugs does not consistently prevent EIA. Exercise avoidance is the most effective treatment. If this is not feasible, exercising with a "buddy" and carrying emergency epinephrine kits is mandatory.
  2. When no cause can be found for anaphylaxis, it is termed idiopathic. Recent reports suggest that 25% of all episodes of anaphylaxis are idiopathic. Many of those affected have underlying allergy or asthma conditions. Extensive allergy testing for foods may uncover an unusual food allergy that is responsible for these reactions. For frequent episodes of anaphylaxis, a physician may recommend a combination of antihistamine, cortisone, and a medication to widen the airways of the lungs (bronchial dilator) to help reduce the severity of attacks.
Medically Reviewed by a Doctor on 6/24/2015

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