Anaphylaxis- why does it happen & how is it treated?

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Anaphylaxis- what causes it & how is it treated?

Authored by Dr Aifric Boylan on 17.04.2018
Medically Reviewed by Dr
Last updated on 20.06.2023

causes

symptoms

treatment

What is anaphylaxis?

Anaphylaxis is a severe life-threatening allergy. Normally, the immune system defends the body against threats such as bacteria and viruses. An allergy is when a person’s immune system reacts abnormally to something it’s exposed to- for example, certain types of food, pollen, animal dander, insect bites or medication. The immune system releases chemicals in response to the trigger.

In mild allergies, this can result in symptoms such as itchy eyes, hives and a runny nose. However, in anaphylaxis the allergic reaction is much more severe and can happen within moments of exposure to a trigger- a wave of chemicals is released by the immune system, quickly affecting a person’s breathing and circulation. It is a medical emergency and usually requires urgent treatment with an adrenaline injection.

How common is anaphylaxis?

It’s thought that around 1 in 100 school children have anaphylaxis, and it’s becoming a more frequent problem.
It’s more common in females than in males.
Anaphylaxis causes 15 deaths per year in Australia.
Death from anaphylaxis is most common where a medication is the trigger.

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What causes anaphylaxis?

Following exposure to the trigger, there is a release of inflammatory substances from certain types of white blood cells, which are part of the body’s immune system
These substances have a rapid effect on various parts of the body, including blood vessels, airways, the heart and the gut, leading to the typical symptoms of anaphylaxis.

Common anaphylaxis triggers include

Foods such as peanuts, treenuts, fish, shellfish and others
Medications- such as antibiotics, aspirin, intravenous contrast
Insect stings and bites- from wasps, bees, fire ants, hornets, yellow jackets
Latex

Rarely, exercise is a cause of anaphylaxis- in some cases, exercise after eating certain foods or exercising in certain temperatures.
A history of certain medical conditions increase the risk of having anaphylaxis, including the presence of allergies, asthma.

What are the symptoms of anaphylaxis?

Symptoms & signs of anaphylaxis include

Tight or constricted breathing
Swelling of the tongue
Difficulty speaking and sometimes a hoarse voice
Swelling or tightness in the throat
Rapid heart rate and low blood pressure
Loss of consciousness/collapse
Pale appearance and floppiness in small children or babies

Sometimes there may be milder signs of allergy before the above symptoms start, which can include:

A tingling sensation around the lips or mouth.
Hives or welts
Abdominal pain and vomiting (although these are viewed as signs of anaphylaxis in the case of insect allergy)

In around 1 in 5 cases, there may be a second bout of anaphylaxis within 12 hours of the first. This is called biphasic anaphylaxis.

Why is anaphylaxis becoming more common?

It’s not certain why anaphylaxis is on the rise, but there are a few theories:

Reduced exposure to germs and infections in early childhood (due to more sanitised living conditions) could lead to a higher risk of allergy. This is sometimes referred to as the “hygiene hypothesis”. Research has shown that children from bigger families, as well as those who have close contact with pets or farm animals are less likely to get allergies and anaphylaxis, which may support this theory.
Delayed exposure to allergenic foods such as nuts and eggs, until later in childhood could be a factor.
Theories have been put forward that taking antibiotics may affect the natural bacteria in the bowel, and that this could have an impact on the immune system.
Some studies have shown that the further a population lives from the equator, the higher the risk of allergies. This may be due to differences in Vitamin D levels (we get most of our Vitamin D from sun exposure).
Different ways of preparing food may be relevant. For example, it appears that roasting peanuts can make them more likely to cause allergy, whereas boiling them reduces the risk. Variations in food preparation may in part explain differences in allergy rates between different countries.

Do complementary or alternative tests for allergies work?

There are many types of alternative therapies that claim to be able to diagnose allergies, but these lack evidence and are best avoided.
Methods which lack evidence include kinesiology, vega testing, hair analysis, cytotoxic food testing, iridology, reflexology, Alcat testing, IgG food allergy testing and Rinkel’s intradermal testing.

How is anaphylaxis diagnosed and treated?

A medical history, examination and allergy tests (bloods and/or skin prick testing) will usually be performed.
If you’ve had an episode of anaphylaxis (or a suspected episode) your GP will usually refer you to an immunology or allergy specialist for assessment and advice.
You’ll need education on how to avoid your trigger- a dietitian specialising in allergies may be helpful if it’s a food trigger.
It’s advisable to wear a medical alert bracelet or necklace, stating that you have anaphylaxis, and the triggers involved
An ASCIA action plan is usually required for children in childcare or school, but is advisable for anyone with a history of anaphylaxis.
An adrenaline (epinephrine) autoinjector is usually prescribed- it’s important to be advised about how and when to use this. If the auto-injector is used, it’s also essential to call an ambulance immediately.
Over time, some allergies may decrease. For example, 20% of children grow out of peanut allergies. Ongoing follow up with an allergy specialist means re-testing can be arranged at appropriate intervals.
Desensitisation therapy (immunotherapy) can be effective in some cases and may be recommended by an allergy specialist.

For more information on allergies and anaphylaxis, speak to your doctor or check out the ASCIA website.

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