Anaphylaxis: everything you need to know

Dr Luke Powles
Associate Clinical Director, Health Clinics Bupa Global and UK
18 April 2023
Next review due April 2026

Anaphylaxis is a life-threatening allergic reaction. It’s vital that someone experiencing it gets immediate treatment. But how do you know if someone has anaphylaxis, and what can you do to help? From anaphylaxis triggers to emergency first aid, I’ll cover everything you need to know here.

A plate of peanuts

What are the most common triggers for anaphylaxis?

There’s a whole range of things that can cause anaphylaxis. It’s not always possible to identify exactly what triggers it. But the most common anaphylaxis triggers include the following.

  • Food. Food reactions can affect both children and adults. Nuts, including peanuts and tree nuts, are the most common food triggers. Others include shellfish, milk, and egg.
  • Drugs. These include anaesthetics, antibiotics (especially penicillin), and non-steroidal anti-inflammatory drugs (NSAIDs).
  • Insect stings. Wasp and bee stings are the main danger, but ant stings and spider bites can also cause an anaphylactic reaction.

What are the signs of anaphylaxis?

If someone is in contact with a trigger, anaphylaxis comes on very quickly - usually within minutes. The affected person will usually start to feel and look unwell, and may appear anxious. They can often sense that something bad is about to happen.

If someone is experiencing anaphylaxis, they will have problems with at least one of the following.

  • Airway. The person’s throat and tongue may swell, making it difficult to breathe or swallow. They may have a hoarse voice and make a high-pitched noise when they breathe in.
  • Breathing. The person may be short of breath. They may wheeze or cough too, and become tired from the effort of breathing.
  • Circulation. The person may go into shock (sometimes called anaphylactic shock). Their pulse rate may become very fast, and they may look pale and clammy (sweaty). A drop in blood pressure can make them feel faint or dizzy, collapse, and lose consciousness.

Someone with anaphylaxis may have other symptoms too, such as skin reactions, stomach pains, and vomiting. But it’s only anaphylaxis if they also get airway, breathing, or circulation problems.

How can I avoid anaphylaxis triggers?

If allergy tests show that you have a particular trigger, your doctor will give you advice about how to avoid it. Here’s a list of what this may include.


  • Check food labels and ingredients on packaging carefully when shopping or buying packaged foods.
  • Be aware that some foods can contain very small traces of an allergen (substances that trigger a reaction). These may be sometimes known under different names. The Allergy UK website has detailed information about particular types of food allergy.
  • If you’re eating out or getting a takeaway, make staff aware that you have a food allergy. Check that they can cater for this.
  • When preparing food at home be sure to wash anything that may have come into contact with an allergen in hot, soapy water. This includes work surfaces.


  • Always tell any health professional that you see about any allergies you have. Don’t expect that the information will be shared between different services.
  • If you have an allergy to NSAIDs, check the ingredients of things like cold medicines carefully. Ask a pharmacist if you’re not sure.
  • Consider wearing an allergy bracelet if you have a severe allergy.

Insect stings

  • Try not to panic if a wasp or bee comes near you – instead, move slowly away.
  • Be careful drinking or eating outside, especially when drinking out of cans.
  • Don’t walk around outside with bare feet.
  • Use insect repellents when you’re outside.
  • Close windows when driving, and preferably at home. You can use fly screens over windows.

How do adrenaline pens help?

If you have an ongoing risk of anaphylaxis, you should be prescribed an adrenaline auto-injector (or ‘pen’), like EpiPen, Emerade or Jext. Adrenaline is the most effective drug for anaphylaxis symptoms. These devices are a quick and safe way of getting the drug. You use them at the first sign that you may have anaphylaxis.

It’s important to carry two auto-injectors at all times, and make sure they’re always in date. Read the instructions that come with your device. Make sure that you, family, friends, or colleagues know exactly how to use it.

What can I do if someone has anaphylaxis?

Anaphylaxis is a medical emergency. If you think you or someone else is experiencing anaphylaxis, follow these steps.

  • If the affected person has an adrenaline auto-injector or pen and knows how to use it, they can do this immediately. They should inject it into the muscle of their upper thigh. If it doesn’t help improve symptoms, they can have a second injection after 5 minutes.
  • Call for an ambulance straight away. Tell the controller that the person has anaphylaxis and follow their instructions. They can give guidance on giving an adrenaline pen if this hasn’t been done already.
  • Help the person into a comfortable position. It’s usually better to lie flat, with legs elevated if they’re feeling faint or dizzy. Someone with breathing difficulties may prefer to sit, or have their shoulders slightly raised.
  • Don’t let the person get up suddenly, walk, or stand, as this can lead to a dangerous fall in blood pressure.
  • If the person stops responding, loses consciousness, or stops breathing, be prepared to start cardiopulmonary resuscitation (CPR).

Anaphylaxis can be scary to deal with if it affects you or a loved one. But the good news is that most people who develop anaphylaxis recover well. The key is to recognise the signs and get treatment quickly. It may just help save a life.

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Dr Luke Powles
Dr Luke Powles
Associate Clinical Director, Health Clinics Bupa Global and UK



Marcella McEvoy, Senior Health Content Editor at Bupa UK

    • Angio-oedema and anaphylaxis. NICE Clinical Knowledge Summaries., last revised October 2022
    • Anaphylaxis and severe allergic reactions. Allergy UK., accessed 10 April 2023
    • Emergency treatment of anaphylaxis. Guidelines for healthcare providers. Resuscitation Council UK., published May 2021
    • Anaphylaxis. BMJ Best Practice., last reviewed 10 March 2023
    • Peanut allergy. Allergy UK., published 6 July 2021
    • Drug allergy. Allergy UK., last accessed 10 April 2023
    • Adrenaline/epinephrine. NICE British National Formulary., last updated 6 March 2023

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