What is Anaphylaxis

Anaphylaxis is a sudden, severe allergic reaction to a substance (called an allergen) that can be life-threatening. Common substances which can cause as severe allergic reaction include bee stings, insect bites, peanuts, eggs, drugs given to the body, etc.
Anaphylaxis suddenly affects the whole body, with severe allergic symptoms including: difficulty breathing, rash, swelling, tummy pain, and reduced blood pressure leading to shock. Anaphylaxis is a medical emergency where immediate treatment is needed to prevent potential death.
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. In anaphylaxis, the immune system must be “primed” by previous allergen exposure. But in anaphylactoid reactions can occur with no previous allergen exposure at all. An example of something that can bring on a severe allergic reaction is radiographic contrast material (the dye injected into arteries and veins to make them show up on an x-ray). Although the mechanism of an anaphylactoid reaction is different, the allergy treatment is the same.

Statistics on Anaphylaxis

Anaphylaxis occurs infrequently. However, it is life-threatening and can occur at any time. Milder forms of anaphylaxis occur much more frequently than fatal anaphylaxis. The frequency of anaphylaxis is increasing and this has been attributed to the increasing number of potential allergens to which people are exposed. In the US, anaphylaxis causes approximately 500-1000 deaths in a year. However the figure is difficult to determine accurately because of underdiagnosis and underreporting.
No major differences have been reported in the incidence and prevalence of severe allergic reactions between men and women. Anaphylaxis occurs in all age groups.
While prior exposure to allergens is essential for the development of true anaphylaxis, severe allergic reactions occur even when no documented prior exposure exists. Thus, patients may react to a first exposure to an antibiotic or insect sting.
Adults are exposed to more potential allergens than are pediatric patients. The elderly have the greatest risk of mortality from severe allergic reactions due to the presence of other diseases usually suffered by elderly population.

Risk Factors for Anaphylaxis

The likelihood of an individual having anaphylaxis is influenced by the following:

  • Age;
  • Gender;
  • Atopy (genetic tendency to develop classic allergic diseases);
  • Route of exposure.

Other risks include prior history of any type of allergic reaction. After an initial exposure to a substance like bee sting toxin, the person’s immune system becomes sensitized to that allergen. On a subsequent exposure, an allergic reaction occurs. Severe allergic reactions are 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 swallowing.
Typically, a severe reaction caused by a food allergy occurs after eating that particular food, even a small bite. Allergy to peanuts is an example. 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.
A severe allergic 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.

Progression of Anaphylaxis

The signs and symptoms of anaphylaxis may occur almost immediately after exposure or within the first 20 minutes after exposure. Rapid onset and development of potentially life threatening symptoms are characteristic markers of anaphylaxis.

Allergic symptoms
may initially appear mild or moderate but can progress rapidly. The most dangerous allergic reactions involve the lungs and/or heart/vessel system.

Symptoms of Anaphylaxis

Common symptoms include:

  • Mild to moderate allergic reaction:
    • Tingling of the mouth;
    • Hives, welts or body redness;
    • Swelling of the face, lips, eyes;
    • Vomiting, tummy pain;
  • Severe allergic reaction (ANAPHYLAXIS):
    • Difficulty and/or noisy breathing;
    • Swelling of the tongue;
    • Swelling or tightness in the throat;
    • Difficulty talking or hoarse voice;
    • Wheeze or persistent cough;
    • Loss of consciousness and/or collapse;
    • Pale and floppy (young children).

How is Anaphylaxis Diagnosed?

The diagnosis of anaphylaxis is based on the signs and symptoms of the patient, and the history of exposure to allergens, and therefore does not rely on laboratory testing.

Prognosis of Anaphylaxis

Anaphylaxis is a severe disorder which has a poor prognosis without prompt treatment. Symptoms, however, usually resolve with appropriate treatment, therefore highlighting the importance of immediate action. There are no long-term effects of anaphylaxis other than the possibility of recurrence or the occurrence of this disease.

How is Anaphylaxis Treated?

Anaphylaxis is an emergency condition requiring immediate professional medical attention. Assessment of the ABCs (Airway, Breathing, and Circulation) should be done in all suspected anaphylactic reactions.
Adrenaline is a drug that should be given by injection without delay. This opens the airways and raises the blood pressure by constricting the blood vessels. Adrenaline comes in multiple formats, one of them called Epi-pen that might be carried by individuals. CPR (cardiopulmonary resuscitation) should be initiated if needed. People with known severe allergic reactions may carry an Epi-Pen or other allergy kit, and should be assisted if necessary.
Emergency interventions by paramedics or physicians may include placing a tube through the nose or mouth into the airway (endotracheal intubation) or emergency surgery to place a tube directly into the trachea (tracheostomy or cricothyrotomy). Treatment for shock includes giving fluids into the patient through the veins and medications that support the actions of the heart and circulatory system. Antihistamines and steroids may be given to further reduce symptoms (after lifesaving measures and adrenaline are administered).

Anaphylaxis Prevention

Prevention involves avoidance of known allergens. Any person experiencing an allergic reaction should be monitored, although monitoring may be done at home in mild cases.
Occasionally, people who have a history of drug allergies may safely be given the offending medication after pretreatment with corticosteroids (prednisone) and antihistamines (diphenhydramine).
People who have a history of allergy to insect bites/stings should be instructed to carry (and use) an emergency kit consisting of injectable adrenaline and chewable antihistamine. They should also wear a Medic-Alert or similar bracelet/necklace stating their allergy.

Anaphylaxis References

  1. Action plans for allergic reactions [online]. Balgowlah, NSW: Australiasian Society of Clinical Immunology and Allergy; 2005 [cited 6 October 2005]. Available from: URL link
  2. Krause RS. Anaphylaxis [online]. Omaha, NE: eMedicine; 2005 [cited 6 October 2005]. Available from: URL link
  3. Pumphrey R. Anaphylaxis: Can we tell who is at risk of a fatal reaction? Curr Opin Allergy Clin Immunol. 2004;4(4):285-90. [Abstract]
  4. Sampson HA, Muñoz-Furlong A, Bock SA,et al. Symposium on the definition and management of anaphylaxis: Summary report. J Allergy Clin Immunol. 2005;115(3):584-91. [Abstract | Full text]
  5. Simons FER, Camargo CA. Anaphylaxis: Rapid recognition and treatment [online]. Waltham, MA: UpToDate; 2005 [cited 6 October 2005]. Available from: URL link

Symptoms of This Disease:

Drugs/Products Used in the Treatment of This Disease:

  • Adrenaline Injection (Adrenaline acid tartrate)
  • Albay Bee/Wasp/Yellow Jacket Venom (Allergen extracts)
  • Allergenic Aqueous Extracts (Allergen extracts)
  • Allergenic Extracts for Scratch & Prick Testing
  • Allpyral Allergen Extracts (Allergen extracts)
  • EpiPen (Adrenaline)
  • Phenergan Injection (Promethazine hydrochloride)
  • Promethazine Hydrochloride Injection BP (DBL) (Promethazine hydrochloride)


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