Anaphylaxis

Introduction

Anaphylaxis is a severe, potentially life-threatening, allergic reaction that can affect many of the systems of the body, including:

  • airways
  • breathing
  • circulation (of the blood)

Anaphylaxis is also known as anaphylaxis shock.

Signs of anaphylaxis include:

  • breathing difficulties
  • dizziness
  • changes to your skin such as itchy skin or a raised red skin rash
  • swelling of certain body parts such as your lips, hands and feet (the medical term for this symptom is angioedema

Read more about the symptoms of anaphylaxis.

What to do

Anaphylaxis should always be treated as a medical emergency. If you suspect that you, or somebody else, is experiencing anaphylaxis you should immediately dial 999 for an ambulance and tell the operator that you think anaphylaxis has occurred.

An injection of an anti-allergy medicine called adrenaline should be give as soon as a reaction is suspected. 

Some people with a previous history of anaphylaxis will have an auto-injector of adrenaline. This should be injected into their thigh muscle and held in place for 10 seconds.

If the person is unconscious, see if they are wearing an allergy alert bracelet which will say if they have an auto-injector.

Read more about the treatment of anaphylaxis.

Outlook

Despite being potentially life-threatening, if treated promptly with adrenaline, most people will make a full recovery and experience no long term complications.

Deaths due to anaphylaxis are rare in the UK numbering around 20-30 per year.

Causes and triggers

Anaphylaxis is your body's immune system overreacting badly to a substance such as food, which it wrongly perceives as a threat. Substances that provoke allergic reactions are known as allergens.

The whole body can be affected, usually within minutes of contact with an allergen, though sometimes the reaction can happen hours later.

The most widely reported triggers of anaphylaxis are:

  • insect stings; particularly wasp and bee stings
  • nuts; particualry peanuts
  • other types of foodstuffs such as milk and shellfish
  • certain medications such as some types of antibiotics

Read more about the causes of anaphylaxis.

Preventing further episodes

If you know what has triggered anaphylaxis it is important to take steps to avoid further exposure to similar triggers.

Though in some cases this is not always possible (for example, wasp and bee stings), or when no obvious trigger can be found.

It is estimated that 1 in 12 people will go on to have another episode of anaphylaxis. Because of this risk you may be prescribed an auto-injector to use in the event of another episode.

Read more about preventing anaphylaxis.

Who is affected

Anaphylaxis is uncommon. It affects people of all ages and is slightly more common in females than males.

People with other allergic conditions, such as asthma or the allergic skin condition atopic eczema, are most at risk of developing anaphylaxis.

Last updated: 03 July 2012

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