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Disease: Anaphylaxis Anaphylaxis
Category: Allergies
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Disease Definition:

Anaphylaxis is an allergic reaction that is severe and potentially life-threatening and can occur within seconds or minutes of exposure to something that a person is allergic to, such as the venom from a bee sting.

A person can go into shock as a result of the flood of chemicals released by their immune system during anaphylaxis. Their blood pressure will drop and their airways will narrow, blocking normal breathing. Some of the causes of anaphylaxis include certain foods, insect venom, some medications and latex.

Anaphylaxis signs and symptoms include a rapid, weak pulse, nausea, vomiting and skin rash.
If left untreated, it can lead to unconsciousness or even death, that’s why a person should immediately go to the emergency room and have an injection of epinephrine.

Work Group:

Prepared by: Scientific Section

Symptoms, Causes


In case a person has been stung by an insect, eaten something that they're allergic to, taken a medication that they're sensitive to, then they are likely to have an anaphylactic reaction. A person will still be at risk of anaphylaxis even if they had experienced only a mild allergic reaction in the past.

The symptoms of anaphylaxis may occur more than half an hour after exposure, but usually, they occur within minutes of exposure to an allergen. These symptoms include:


  • Constriction of the airways and a swollen tongue or throat, which can cause wheezing and trouble breathing.
  • Skin reactions including hives and itching, flushed or pale skin. These symptoms are almost always present with anaphylaxis.
  • Nausea, vomiting or diarrhea
  • Dizziness or fainting
  • A weak and rapid pulse

The local emergency number should be immediately called in case someone has a severe allergic reaction.
In case the person having the attack happens to carry an epinephrine auto-injector, they should take the shot immediately. The epinephrine injection will improve the symptoms of anaphylaxis. However, to make sure that they won't return, the person should visit the emergency room.

In case a person has had a severe allergy attack, or any of its signs of symptoms, they should see a doctor who specializes in allergies and immunology because evaluation, diagnosis and long-term treatment of anaphylaxis are complicated.


When a foreign or harmful substance enters the body, the immune system produces antibodies that defend against these substances, which could be a bacterium or a virus.
However, the immune system sometimes overreacts to substances that shouldn't cause an allergic reaction and when this happens, the immune system sets off a chemical chain reaction, which leads to allergy symptoms. Although some people have a severe allergic reaction that can lead to anaphylaxis, but in most people, allergy symptoms are not life-threatening.

Depending on what a person is allergic to, a number of allergens can trigger anaphylaxis, such as:


  • Foods, including fish, shellfish, peanuts, milk, eggs and tree nuts, such as pecans and walnuts.
  • Certain medications, such as penicillin.
  • Insect stings from bees, yellow jackets, wasps, fire ants and hornets.

Some of the least likely causes of anaphylaxis are:


  • Muscle relaxants that are used in general anesthesia
  • Latex
  • Exercise: This condition varies from person to person, for instance, aerobic activity such as jogging can trigger anaphylaxis in some people, while in others a less intense physical activity can trigger it, such as gardening. Exercising when the weather is cold, hot or humid, or eating certain foods before exercise is also linked to anaphylaxis in some people. If a person with this condition wants to exercise anyway, they should consult their doctor about the needed precautions.

In some rare cases, anaphylaxis is caused by IV (intravenous) contrast that is used in certain X-ray imaging tests, acetylsalicylic acid and other nonsteroidal anti-inflammatory drugs, such as naproxen, or ibuprofen. This type of reaction isn’t triggered by allergy antibodies, even though it is similar to allergy-induced anaphylaxis.

A person could be tested in order to identify the offending allergen in case they have no idea what triggers their allergy attack.
Idiopathic anaphylaxis is the condition in which the exact cause of anaphylaxis can't be identified.



Anaphylaxis is a life-threatening condition because when a severe anaphylactic attack occurs, the person's breathing or heartbeat may stop. In this case, a patient will need CPR (cardiopulmonary resuscitation) in addition to other emergency treatments right away.


In case someone's breathing or their heartbeat stops during an anaphylactic attack, an emergency medical team may perform CPR, and give the patient these medications:


  • Oxygen, in order to help compensate for restricted breathing.
  • Epinephrine, which is adrenaline, to reduce the body’s allergic response
  • IV (intravenous) antihistamines and cortisone, to reduce inflammation of the air passages and improve breathing
  • Steroid medications to prevent or treat prolonged anaphylaxis symptoms
  • A beta agonist, in order to relieve breathing symptoms, such as albuterol (salbutamol)

The signs and symptoms of shock caused by anaphylaxis include pale, cool and clammy skin, trouble breathing, confusion and loss of consciousness as well as weak and rapid pulse. Now if a person is with someone who is having an allergic reaction and shows the signs mentioned above, even if they're not sure, they should follow these steps:

  • Calling the local emergency number
  • Checking the patient's pulse, and performing CPR or other first aid measures if necessary
  • In case the affected person happens to carry medication to treat an allergy attack, such as an epinephrine auto-injector or antihistamines, they should be given the shot right away.

Many people with allergies, who are at risk of anaphylaxis, carry an auto-injector. This device injects a single dose of medication when pressed against the thigh. The epinephrine should be replaced before its expiration date to work properly.  

If a person has allergies, he/she should make sure to know how to use an auto-injector and that the people closest to him/her also know how to administer the drug, so that if those people happen to be with that person during an anaphylactic emergency, they could save his/her life. In the emergency room, the medical team may give the patient another epinephrine injection as well as other medications to treat the symptoms.

In case a person's allergic reaction is triggered by insect stings, they may undergo immunotherapy, which is a series of allergy shots to reduce the body’s allergic response and prevent a severe reaction in the future.

However, in most of the other cases there’s no way to treat the underlying immune system condition that can lead to anaphylaxis. But there are certain steps that could be taken in order to be prepared when an attack occurs, and sometimes even prevent it.

If a person carries with him/her a self-administered epinephrine, they can inject themselves with it during an attack. A person may also be recommended to take prednisone or antihistamines.


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