What is Anaphylaxis?

Anaphylaxis (pronounced an-uh-fuh-lak-sis) is a very severe and serious allergic reaction.  The term Anaphylaxis comes from the Greek words ἀνά ana, against, and φύλαξις phylaxis, protection.  When a person is suffering from Anaphylaxis (or Anaphylactic Shock) it needs to be treated as a matter of urgency as the symptoms of respiratory obstruction and shock develop rapidly, they must receive treatment immediately.

An allergic reaction is due to your immune system over-reacting to the presence of a foreign body.  It treats something that would normally be harmless as a threat.  An anaphylactic reaction is caused by the sudden release of chemical substances, including histamine, from cells in the blood and tissues where they are stored. The release is triggered by the reaction between the allergic antibody (IgE) and the substance (allergen) causing the anaphylactic reaction. This mechanism is so sensitive that minute quantities of the allergen can cause a reaction. The released chemicals act on blood vessels and cause swellings in the mouth, lips, tongue and anywhere on the skin.  There is a fall in blood pressure and, in asthmatics; the effect is mainly on the lungs.


 The first documented case of anaphylaxis was in 2641 BC, when King Menes of Egypt died from a Wasp sting.  The first fatal reaction to peanuts was described by a Canadian researcher Dr Evans in 1988.


Signs and Symptoms of Anaphylaxis

Image By Mikael Häggström (Own work) [CC0], via Wikimedia Commons

What are the symptoms of Anaphylaxis?

It is important to recognize the symptoms of anaphylaxis so you know when it is necessary to seek lifesaving assistance for yourself or for someone else.

It is very important to remember that different people will experience different symptoms during an anaphylactic episode, so how one person reacts will not always be the same as how another person suffering from anaphylaxis will react.  Please also bear in mind that you do not have to have all of the listed symptoms to be experiencing anaphylaxis.

You may have some or all of the following symptoms:

  • your throat and mouth swells
  • you find it hard to swallow or speak
  • your heart rate changes
  • you find it hard to breathe – due to severe asthma or throat swelling
  • you have hives (nettle rash) anywhere on the body, especially large hives
  • your skin is flushed all over
  • stomach cramps, nausea and vomiting
  • you feel sudden weakness (drop in blood pressure)
  • you have a sense of impending doom
  • you collapse or fall unconsciousness

A patient would not necessarily experience all of these symptoms.

What can cause anaphylaxis?

The most common causes of anaphylactic shock are:

  • peanuts
  • tree nuts such as almonds, walnuts, cashews, brazil nuts
  • sesame
  • fish
  • shellfish
  • dairy products
  • eggs
  • soya
  • wasp or bee stings
  • natural latex (rubber)
  • penicillin and other drugs or injections

Severe allergic reactions to fresh fruit, such as kiwis and apples, are increasing.  In some people, exercise can trigger a reaction – either on its own, or combined with other factors such as eating a certain food or drugs (eg. aspirin).  ‘Idiopathic anaphylaxis’ has no obvious trigger.

Why does anaphylaxis occur?

Any allergic reaction, including the most extreme form, anaphylactic shock, occurs because the body’s immune system reacts inappropriately in response to the presence of a substance that it wrongly perceives as a threat.

How is anaphylaxis treated?

Anaphylaxis can be treated with an injection of adrenaline (also called epinephrine).  Adrenaline acts quickly to constrict blood vessels, relax your lungs to improve breathing, stimulate your heartbeat and help to stop swelling around your face and lips.  This swelling is called angioedema.  If you have a serious reaction, the normal medical treatment is an immediate injection of adrenaline. If you have suffered from anaphylaxis you should speak to your allergy specialist about being prescribed with a preloaded injector pen, the most commonly prescribed are EpiPen, Anapen and Jext.

Every time you have a serious reaction, you should receive adrenaline and call an ambulance. You will need to go to hospital for more medical treatment and observation.  This is important, because the reaction may happen again some time later. Because an anaphylactic reaction can be fatal, you must get clear guidance from your doctor about how and when to inject adrenaline.  You should know the range of symptoms so you can tell when a reaction is serious.

At risk from anaphylaxis?

Unfortunately, if you have previously suffered a bad allergic reaction then any future reaction is also likely to be severe.  If you have reacted to foods such as nuts, seeds, fish and shellfish then even mild symptoms shouldn’t be ignored as future reactions may be severe.  If you also suffer from asthma as well as allergies, then it is very important that you are seen by an allergy specialist because this puts you in a higher risk category.

If you have any type of allergic reaction, you should see your GP.  You may find it helpful to look on our “Find Allergy Clinic” tool to locate your nearest allergy clinic, and take this information along to your G.P. appointment.