Anaphylaxis is the most severe form of allergic reaction and is potentially life threatening. It must be treated as a medical emergency, requiring immediate treatment and medical attention.

Life-threatening signs and symptoms include:

  • difficult/noisy breathing
  • swelling of the tongue
  • swelling or tightness in the throat
  • difficulty talking or hoarse voice
  • wheeze or persistent cough
  • persistent dizziness or collapse
  • pale and floppy (young children).

These symptoms are life-threatening and require urgent medical attention. Administer adrenaline if available and call 111. Do not drive yourself to hospital even after giving yourself adrenaline.

Causes of anaphylaxis

Anaphylaxis is a whole-body allergic reaction in response to exposure to an allergen. It can cause airways to tighten and restrict breathing and other life-threatening symptoms. Common triggers of anaphylaxis include:


Milk, eggs, peanuts, tree nuts, sesame, fish, shellfish, wheat and soy are the most common food triggers, which cause 90% of allergic reactions; however, any food can trigger anaphylaxis. It is important to understand that in some people even very small amounts of food can cause a life-threatening reaction. Some extremely sensitive individuals can react to just the smell of particular foods being cooked (ie, fish) or even kissing someone who has eaten the food they’re allergic to.

Insect venom

Bee and wasp are the most common causes of anaphylaxis from insect stings.


Medications, both over-the-counter and prescribed, can cause life-threatening allergic reactions. Individuals can also have anaphylactic reactions to herbal or 'alternative' medicines.


Other triggers such as latex or exercise-induced anaphylaxis are less common and occasionally the trigger cannot be identified, despite extensive investigation.

Symptoms of anaphylaxis

The signs and symptoms of anaphylaxis usually occur within the first 20 minutes to two hours after exposure. Rapid onset and development of potentially life-threatening symptoms are characteristic markers of anaphylaxis.

Allergic symptoms may initially appear mild or moderate but can progress rapidly. The most dangerous allergic reactions involve the respiratory system (breathing) and/or cardiovascular system (heart and blood pressure).

Mild to moderate allergic reaction

  • tingling of the mouth
  • hives, welts or body redness
  • swelling of the face, lips, eyes
  • vomiting, abdominal pain.

Severe allergic reaction

The following symptoms are life-threatening and require urgent medical attention administer adrenaline (if available) and call 111:

  • Airway
    • swelling of tongue
    • hoarse voice
    • swelling or tightness in the throat
    • difficulties swallowing.
  • Breathing
    • difficulty and/or noisy breathing
    • wheeze or persistent cough.
  • Circulation
    • shock (pale, clammy)
    • racing heart
    • persistent dizziness or collapse
    • loosing consciousness
    • pale and floppy (young children).


After experiencing an anaphylactic reaction and getting emergency medical care in hospital, you need to see a specialist to find out what your triggers are and work out an anaphylaxis action plan.

Exposure to known allergens, followed by life-threatening airway, breathing or circulatory problems strongly indicates anaphylaxis. If there are no known allergens or you are not aware that exposure has occurred, anaphylaxis may be suspected if all three of the following are met:

  • allergic symptoms start suddenly and get worse quickly
  • life-threatening airway, breathing or circulatory problems (see Symptoms above)
  • changes to skin or mucosa (linings of mouth and nose) – these may be hard to see.

Food allergy diagnosis

A person who is suspected of having a food allergy should obtain a referral to see an allergy specialist for correct diagnosis, advice on preventative management and emergency treatment. Those diagnosed with severe allergy must carry emergency medication as prescribed as well as an Anaphylaxis action plan signed by their doctor.

Food allergic children who have a history of eczema and/or asthma are at higher risk of anaphylaxis.


Anaphylaxis is a preventable and treatable event. Knowing the triggers is the first step in prevention. Children and caregivers need to be educated on how to avoid food allergens and/or other triggers. However, because accidental exposure is a reality, you and your child need to be able to recognise symptoms of an anaphylaxis and be prepared to administer adrenaline according to your anaphylaxis action plan. Ask your doctor for more information on an anaphylaxis action plan


Administration of adrenaline is the best treatment of anaphylaxis. Adrenaline can be easily given using an auto-injector such as an EpiPen. The EpiPen injects a single, pre-measured dose of adrenaline into the muscle. If you have a history of anaphylaxis then you should consider carrying an EpiPen with you. Deaths from anaphylaxis are more common away from home and when adrenaline is either not used or delayed. Read more about the EpiPen.

Don't use antihistamines

Don’t use antihistamines to treat anaphylaxis — prompt administration of adrenaline is the only treatment for anaphylaxis. Anaphylaxis is a potentially life threatening, severe allergic reaction and should always be treated as a medical emergency. Read more about severe allergic reaction Choosing Wisely, NZ


Once you have had an anaphylactic reaction you will be referred to a specialist to help you work out what your triggers are. This may involve allergy testing or food/drug challenge.

Knowing what your triggers for anaphylaxis are essential. In many cases avoidance is the only way to prevent anaphylaxis. Your specialist will help you work out ways to reduce the risk of anaphylaxis. This usually includes writing up an emergency anaphylaxis action plan.

You will need to have regular reassessment, to check if the allergy is still present and to make sure your prevention plan is working for you.

Learn more

A range of anaphylaxis resources Allergy New Zealand
Information on adrenaline auto-injector devices Allergy New Zealand

Credits: Health Navigator Editorial Team. Reviewed By: Penny Jorgensen, Allergy Advisor, Allergy New Zealand Last reviewed: 12 Apr 2018