What is anaphylaxis?
Anaphylaxis (pronounced an-a-fill-ax-is) is a severe and potentially life-threatening allergic reaction affecting more than one body system such as the airways, heart, circulation, gut and skin. Symptoms can start within seconds or minutes of exposure to the food or substance you are allergic to and usually will progress rapidly. On rare occasions there may be a delay in the onset of a few hours.
Anaphylaxis is potentially life-threatening, and always requires an immediate emergency response.
What are the causes of anaphylaxis?
The common causes of anaphylaxis include foods such as peanuts, tree nuts, milk, eggs, shellfish, fish, sesame seeds and kiwi fruit. Non-food causes include wasp or bee stings, natural latex (rubber), and certain drugs. Each year in the UK, approximately 500 people have severe allergic reactions to an anaesthetic drug, which translates to one in every 10,000 procedures. In some people exercise can trigger a severe reaction – either on its own or in combination with other factors such as a food.
Sometimes the cause of the reaction is not found. Such reactions may be labelled “idiopathic anaphylaxis” (cause unknown). This does not mean the condition is psychological, though emotional stress can sometimes worsen a reaction.
What are the symptoms of anaphylaxis?
Most healthcare professionals consider an allergic reaction to be anaphylaxis when it involves a difficulty in breathing or affects the heart rhythm or blood pressure. Any one or more of the following symptoms may be present. These are often referred to as the ABC symptoms:
There may be a dramatic fall in blood pressure (anaphylactic shock). If that happens, the person may become faint and dizzy, or in the case of a child they may become floppy. This may lead to collapse, unconsciousness and – on rare occasions – death.
In addition to the ABC symptoms listed above, the following symptoms may occur:
• Widespread flushing of the skin
• Nettle rash (otherwise known as hives or urticaria)
• Swelling of the skin (known as angioedema) anywhere on the body (for example, lips, face).
• Abdominal pain, nausea and vomiting
Those symptoms can also occur on their own. In the absence of the more serious ABC symptoms listed above, the allergic reaction may be less severe but you should watch carefully in case ABC symptoms develop.
Watch Professor John Warner OBE, Emeritus Professor of Paediatrics, Imperial College London, explain anaphylaxis and allergy:
What increases the risk of a severe reaction?
There are times when you may be particularly vulnerable and at increased risk of a severe reaction. Times when you need to be particularly careful to avoid the culprit allergen include:
• If you have asthma that is poorly controlled
• If you are suffering from an infection, or have recently had one
• If you exercise just before or just after contact with the allergen
• If you are also suffering from hay fever
• During times of emotional stress
• If you have been drinking alcohol
• If you have taken a ‘non-steroid anti-inflammatory drug’ (NSAID) such as aspirin or ibuprofen.
What is the treatment for a severe reaction?
Pre-loaded auto-injectors containing adrenaline are prescribed for people believed to be at risk of anaphylaxis. Adrenaline is referred to in some countries as epinephrine, which is the internationally recognised term for adrenaline.
Because severe allergic reactions can occur rapidly, the prescribed auto-injectors must be readily available at all times. The injection should be given as soon as any symptoms of anaphylaxis are present. If in doubt, give adrenaline. A second dose should be given after 5-10 minutes if symptoms of anaphylaxis remain, or if there is any doubt about whether the symptoms have improved.
An ambulance must be called immediately following an injection of adrenaline, even if there is immediate improvement. The emergency service operator must be told the person is suffering from anaphylaxis and needs to be attended by paramedics.
In our view it is important to ensure that you carry two adrenaline auto-injectors at all times which are in date and of the correct dose. To read more about adrenaline, including the need to carry two, click here.
1. If you suspect you have an allergy, see your GP as soon as possible. Many GPs are well informed about allergy and can make a diagnosis to decide whether you need adrenaline or not. In many cases, the GP will need to refer you to an NHS allergy clinic.
2. If you are at risk of the severe form of allergy – anaphylaxis – you are likely to be prescribed adrenaline. This must be available at all times.
3. If you have asthma as well as allergies, make sure your asthma is well managed. If you have poorly controlled asthma, there is a higher likelihood of any allergic reaction becoming severe. See your GP or asthma nurse for advice on this crucial point and to obtain an asthma management plan to help you self-manage.
This fact sheet has been peer reviewed by Dr Alexandra Croom, consultant allergist based in the Respiratory Department at Glenfield Hospital, Leicester.
Disclaimer – The information provided in this Factsheet is given in good faith. Every effort has been taken to ensure accuracy. All patients are different, and specific cases need specific advice. There is no substitute for good medical advice provided by a medical professional.
About the Anaphylaxis Campaign: Supporting people at risk of severe allergies
The Anaphylaxis Campaign is the only UK wide charity to exclusively meet the needs of the growing numbers of people at risk from severe allergic reactions (anaphylaxis) by providing information and support relating to foods and other triggers such as latex, drugs and insect stings. Our focus is on medical facts, food labelling, risk reduction and allergen management. The Campaign offers tailored services for individual, clinical professional and corporate members.
All the information we produce is evidence based or follows expert opinion and is checked by our expert clinical and research reviewers. If you wish to know the sources we used in producing any of our information products, please let us know, and we will gladly supply details.
Publication Date: March 2020
Next Review Date: March 2023