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Anaphylaxis, or anaphylactic shock, is the most severe allergic reaction that can rapidly become life threatening if it isn’t treated immediately. Anaphylaxis often affects more than one body system, including skin, respiratory, gastrointestinal and cardiovascular. This severe allergic reaction generally occurs within 20 minutes to 2 hours after exposure to an allergen.

How does it work?

An allergic reaction occurs when a person’s immune system overreacts to a substance or ‘trigger’ that is generally harmless to other people. This substance is called an allergen. When someone comes into contact with something they are allergic to, their immune systems responds by creating an antibody to attack the allergen, which then sets off a range of immune system reactions. People who have anaphylaxis have the most severe type of allergic reaction. This means that their immune system reacts to such an extent that it becomes dangerous to them and can result in death if it is not treated as a medical emergency.

In an anaphylactic reaction the body suddenly releases chemical substances, such as histamine, that are stored in the cells of blood and tissue. This sudden release is caused by the reaction between the antibody and the allergen. The chemicals released from the cells cause swelling by acting on blood vessels. These chemicals also cause other problems such as a fall in blood pressure. People with anaphylaxis are usually so sensitive to their allergens that even a minute amount can trigger this dangerous reaction.

Why is Anaphylaxis so dangerous?

Anaphylaxis is treated as a medical emergency because many of the symptoms can quickly become life threatening. These symptoms include:

  • Tightness of the throat from swelling
  • Difficulty breathing
  • Tongue & facial swelling
  • Hoarse voice or difficulty speaking
  • A wheeze or persistent cough
  • Collapse or falling unconscious
  • Becoming pale or floppy (young children)
  • Abdominal pain & vomiting
  • Hives, welts & body redness

What are the more subtle signs of anaphylactic shock?

As well as severe symptoms, there are also a range of less dangerous anaphylactic symptoms including:

  • Flushed skin
  • Hives
  • Nausea and vomiting
  • Stomach pain
  • Sudden feeling of weakness
  • Swelling of the face, lips and eyes

Although these symptoms are less alarming, they should be treated with just as much urgency as more severe symptoms. Anaphylactic shock can quickly escalate and the earlier it is treated the better.

What are the common triggers?

There are a range of allergens that can cause someone to go into anaphylactic shock. The most common of these include:

  • Food
  • Milk
  • Eggs
  • Peanuts
  • Tree nuts
  • Sesame
  • Fish
  • Shellfish
  • Wheat
  • Soy

Venom from Bites and Stings

  • Bee
  • Wasp
  • Ant stings


  • Over the counter
  • Prescribed
  • Herbal/alternative

How is it treated?

Anaphylaxis is not curable, however it is preventable and treatable. Adrenaline auto-injectors, such as Epipen and Anapen, are carried by those who are at risk. These auto-injectors are designed to be used by anyone, including a friend, childcare worker, parent, teacher, passerby or the patient.

The most common site to inject someone who might be going into anaphylactic shock is directly into their thigh. The adrenaline will reduce the effects of the reaction by constricting blood vessels, relaxing muscles in the lungs to improve breathing, stimulating the heart beat and helping to reduce swelling. If you suspect someone could go into anaphylactic shock you should also call 000 immediately to ensure professional medical help is given as soon as possible.

If you are required in your workplace to be certified in first aid for asthma, check out our Asthma & Anaphylaxis training course.

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