Intolerance, allergy or anaphylaxis?

If you have ever experienced a bad reaction to something you’ve eaten, or touched, or an insect sting, you know it can be unpleasant. But what’s actually going on when this happens? Well, it depends on whether you have an allergy to the substance that caused the reaction, or just an intolerance.

What’s the difference between intolerance and allergy?

It can be very difficult to tell, unless you see a doctor for a proper diagnosis. This is because some symptoms of food intolerance can be similar to symptoms of mild – moderate food allergic reactions. For example, someone with an allergy to cow’s milk may feel bloated and nauseous after drinking it, and so might someone who has an intolerance. However, when you have an allergy to a certain substance, it causes a very specific set of reactions to occur in your body, involving your immune system. Food intolerances do not involve the immune system and do not cause anaphylaxis.

Different people can react differently to the same substance. And in the case of allergies, it’s possible that a person’s reaction to a substance can become more severe the next time they encounter that substance. That’s why it’s important to see a doctor to work out what is going on.


Mild to severe

Allergic reactions can be mild, moderate or severe. Most allergic reactions have mild to moderate symptoms, generally involving just one part of the body. For example, if you have a food allergy you probably experience gastrointestinal symptoms; and if you are allergic to something like latex your skin is most likely to show the results when you touch it. However, if you have a severe allergic reaction, many different parts of the body can be affected at the same time.

A very severe allergic reaction is called anaphylaxis – pronounced a-na-fi-LAX-is – and it can be life-threatening. Anaphylaxis occurs when the body reacts very strongly to an allergic trigger, leading to dangerous symptoms, such as difficulty breathing or loss of consciousness. Where an allergic reaction is often localised to one particular part of the body, anaphylaxis can often involve many different types of symptoms and parts of the body. Anaphylaxis usually occurs 20 minutes to 2 hours after exposure to a trigger.1

The way you react to a trigger can change over time. So, even if you have only ever had mild or moderate symptoms in the past, it does not mean you are not at risk of anaphylaxis. For example, one study has shown that among a group of children with peanut allergy, nearly half experienced anaphylaxis when exposed despite only ever having a mild-to-moderate reaction previously.Therefore it is recommended that you see your allergy specialist for regular review as directed by your specialist. You should also see your allergy specialist if you experience a severe allergic reaction.

In an anaphylaxis emergency

  • 1. Lay the person flat.
  • 2. Administer an adrenaline auto-injector (if they have one) into outer mid thigh and hold for 10 seconds.
  • 3. Phone 000 in Australia or 111 in NZ and ask for an ambulance.
  • 4. Commence CPR if necessary.

Allergies and anaphylaxis on the rise

Allergy is very common, and it is increasing. In the past few decades the rate of allergic disease in Australia and New Zealand has approximately doubled,3 and one in three people can now expect to develop an allergy.4 Anaphylaxis is also on the rise, in just the last 10 years, the number of people admitted to hospital with anaphylaxis because of food allergies has doubled.5 In young children, the rate has increased 5 times.5

Anaphylaxis is ALWAYS a medical emergency. Approximately three out of four people who have experienced an anaphylactic reaction will have another one.6 Each year in Australia, around 10 people die of anaphylaxis.5







3 in 4 people who have experienced an anaphylactic reaction will have another one.6

1. Allergy and Anaphylaxis Australia. What is anaphylaxis? Available at Accessed 28 Nov 2013.
2. Vander Leek TK, et al. J Paediatr 2000;137(6):749–755.
3. Australasian Society of Clinical Immunology and Allergy (ASCIA). AIIDA report 2013. Available at Accessed 28 Nov 2013.
4. Australasian Society of Clinical Immunology and Allergy (ASCIA). What is allergy? Available at Accessed 28 Nov 2013.
5. Australasian Society of Clinical Immunology and Allergy (ASCIA). Food allergy and anaphylaxis update 2013. Available at Accessed 28 Nov 2013.5.
6. Kemp SF et al. Arch Intern Med 1995;1749–1754.