Anaphylaxis symptoms, causes, and treatment

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Everything you need to know about anaphylaxis, a severe and potentially life-threatening reaction to a trigger such as an allergy.

By Dr Juliet McGrattan (MBChB)

Anaphylaxis is the severest form of allergic reaction. It is potentially life threatening. According to The National Institute for Health and Care Excellence (NICE), around 20 people in the UK die each year from anaphylaxis.

Award-winning author and running health expert Dr Juliet McGrattan looks at anaphylaxis symptoms, causes, treatments and shares first aid tips on what to do in an emergency situation:

What is anaphylaxis?

When the body is exposed to certain triggers, also called allergens, the immune system can sometimes recognise them as a threat. In anaphylaxis, the body overreacts and allergic symptoms rapidly develop and spread through the body. Anaphylaxis can result in collapse, unconsciousness and death if treatment is not received quickly.

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When contact is made with the allergen, immune cells (mast cells and basophils) react and release a range of chemicals stored inside them. This includes histamine which leaks into the blood stream and triggers the allergic symptoms.

What causes anaphylaxis?

Anaphylaxis can be caused by something you know you are allergic to such as a certain food or medication. It’s most common for anaphylaxis to happen straight after contact with the allergen but there can be a delay of several hours. Sometimes it can come completely out of the blue and may not have an obvious cause at all. This is called idiopathic anaphylaxis.

Common causes of anaphylaxis include:

  • Foodstuffs– nuts (especially peanuts), wheat, cow’s milk, eggs, soy, shellfish, pulses.
  • Insect venom– wasp and bee stings.
  • Medications– antibiotics, non-steroidal anti-inflammatory drugs including aspirin, general anaesthetic drugs, dyes used during medical scanning.
  • Other– latex.

Anaphylaxis signs and symptoms

Symptoms of anaphylaxis and their severity vary but they can develop very quickly and include:

  • Itching
  • Skin rashand redness (hives or wheals, also called urticaria)
  • Swelling (angioedema) commonly of the tongue, lips and throat
  • Difficulty breathing
  • Fast breathing
  • Wheezing
  • Hoarse voice
  • Difficulty swallowing
  • Heart racing
  • Palpitations
  • Low blood pressure
  • Dizziness
  • Sweating
  • Nausea or vomiting
  • Abdominal pain
  • Acute anxiety
  • Confusion
  • Feeling faint
  • Collapse
  • Unconsciousness

Anaphylaxis risk factors

If you have had an allergic reaction to something previously or you have a ‘hypersensitivity’ condition such as asthma, then you are more likely to have anaphylaxis.

Adults and children can both be affected. Children have more general allergic reactions than adults but adults are more likely to have anaphylaxis.

The most common triggers in children are food – peanuts, cow’s milk and eggs. Insect stings and medications cause the most anaphylaxis in adults.

Anaphylaxis diagnosis

It is the nature of the symptoms and the speed that they progress that is the key to diagnosing anaphylaxis. You become very ill very quickly. Sometimes blood tests can be used to confirm the diagnosis but emergency treatment always takes priority.

Anaphylaxis first aid

To help someone who is having an anaphylactic reaction, recognise that this is an emergency situation and treatment is needed as fast as possible:

  1. Stay calm and reassure the patient.
  2. People known to have severe allergies may be carrying an adrenaline auto injector (AAI). A common brand is the Epipen. They may be able to give this themselves or require you to do it for them. Give it into the upper, outer thigh. You can find out how to use AAIs Giving the AAI is the most important thing to do and you should do it first.
  3. If you don’t know the person, check to see if they are wearing any medical alert jewellery that will tell you if they have severe allergies.
  4. Dial 999 for an ambulance, even if you have given the injection. Tell the call handler that you think it is anaphylaxis.
  5. Get rid of the allergen if you know what it is. For example, remove the bee sting (taking care not to squeeze it because this will release more venom) or wash out bits of nut from the mouth if you can.
  6. Get the person to lie down flat while you wait for the ambulance.
  7. If they are pregnant, put a pillow under their right hip to tip their bump over to the left – lying completely flat can be harmful.
  8. If more than five minutes have passed and they are not getting better or have begun to get worse, then use a new AAI and give them a second dose.
  9. Keep talking to them and reassuring them to help them stay calm. If they become unconscious, put them into the recovery position.
  10. If they stop breathing, you should start cardiopulmonary resuscitation (CPR). Watch an online video or attend a course to learn how to do CPR. St John’s Ambulanceare a great resource.

Anaphylaxis treatments

The most important factors in any unwell person are the ABC: this stands for airway, breathing and circulation. They are crucial for survival. Anaphylaxis affects all of these and this results in a significant risk to life from anyone who has an anaphylactic reaction. The airway becomes blocked by swollen tissues, breathing is difficult due to spasm in the lungs and circulation collapses.

Treatment is focused on reversing and supporting the ABC. The faster the treatment, the better the outcome.

In hospital treatments include:

  • Adrenaline – given by injection into a muscle or directly into a vein by a specialist if required.
  • Oxygen via a mask.
  • Intra-venous fluids.
  • Anti-histamine injections.
  • Steroid injections.
  • Asthmamedications by mask or injection to relieve airway spasm if appropriate.

All patients will be closely monitored to ensure they are improving. If the airway is blocking off they may be intubated (a tube is put into the windpipe) and put on a ventilator. Patients with severe reactions or those that are unstable will be taken to the intensive care unit (ICU).

The number of people suffering from anaphylaxis seems to be increasing year upon year. Thankfully the number of people that die from it seems to be stable.

What happens after anaphylaxis?

You will need to stay in hospital for observation until the doctors are happy that your risk from anaphylaxis has passed. The length of time will vary from six hours to several days if you were very unwell.

If you had to have emergency treatment for anaphylaxis, you should be referred to a specialist allergy clinic.

You will be given an adrenaline auto injector (AAI) and taught how and when to use it. You should keep two of these with you at all times.

If you have had an anaphylaxis due to insect venom, you may be offered venom immunotherapy which involves being exposed to tiny amounts of venom to help your body get used to it and prevent a further anaphylaxis.

Anaphylaxis prevention

The most important way to prevent anaphylaxis is to identify and avoid the allergens triggering it. This might involve having some allergy tests such as skin prick tests and blood tests at an allergy clinic to find out what you are allergic to.

The steps you take to avoid the allergen will vary according to what it is:

  1. Wasp and bee stings: take care when eating and drinking outside, avoid walking bare foot and use an insect repellent.
  2. Food allergies: if you have food allergies, read the ingredients list on food labels, when eating out advise the staff of your allergies.
  3. Medications: discuss your allergies with the health care provider who is prescribing for you.

If you are at risk of anaphylaxis don’t become blasé, remember that anaphylaxis is severe:

  • Always carry two AAIs with you at all times.
  • Show your friends and family how to use an AAI.
  • Make sure that you check the AAIregularly to ensure it isn’t out of date.
  • Put a reminder on your calendar as to when you need to order another prescription.
  • If in doubt use it! It is better to treat an allergic reaction as early as possible.
  • Consider wearing medical alert jewellery.

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