Anaphylaxis, or anaphylactic shock, is a sudden catastrophic
allergic reaction involving the whole body. Immediate medical
treatment is essential, without it your heart and circulation may
fail and you could die.
What's the cause?
No one is sure why some people get anaphylaxis and some don't.
It usually happens to people who are known to have an allergy
and the most common cause of anaphylaxis is eating a food to
which you are allergic.
Peanuts and tree nuts (such as almonds, brazil nuts, hazelnuts
and walnuts) are the foods most likely to provoke a reaction.
Anaphylaxis can also be brought on by fish, shellfish, eggs and
dairy products. Even eating a tiny amount of a particular food
can cause anaphylaxis.
Allergy to venom from bee and wasp stings can cause the reaction
too, as can allergy to latex and drugs such as antibiotics.
What are the symptoms?
The initial reaction is swelling and itching of the area the allergen has
entered. So food initially causes swelling and itching of the mouth
and throat, while a wasp sting will cause intense itching and swelling
around the bite.
A generalised reaction rapidly follows and an itchy rash spreads over
the whole body. The face and soft tissues begin to swell and breathing
The person becomes very agitated – people describe a 'feeling of
impending doom' - and their blood pressure begins to drop.
At this point the victim collapses and loses consciousness.
These symptoms can develop within a few minutes of contact
with the allergen.
What's the treatment?
Anaphylaxis requires emergency treatment because the symptoms
of respiratory obstruction and shock develop so quickly. An injection
of adrenaline is given to raise blood pressure, relieve breathing
difficulties and reduce swelling.
As long as this is done promptly, people normally recover quickly
but anyone who's had anaphylaxis should go to hospital for
observation regardless. This is because they may need further
treatment - such as antihistamines, corticosteroids and occasionally
oxygen and intravenous therapy - when the adrenaline wears off.
Providing first aid
Although emergency medical help is essential, there are things that
must be done to improve survival chances. If the person is conscious
and having breathing difficulties, help them sit up. If they are shocked
with low blood pressure, however, they are better off lying flat with
their legs raised.
If the person is unconscious, check their airways and breathing and
put them in the recovery position.
If you know that the person is susceptible to anaphylaxis, ask if they
carry a preloaded adrenaline syringe. If necessary, help the person
inject it into the muscle of the thigh.
Then dial 999 for an ambulance and tell the controller that you think
the person may have anaphylaxis. If available, antihistamines and
steroids should also be given.
To find out about training and courses in your area, contact your
nearest branch of the British Red Cross or St John Ambulance
(or St Andrew's Ambulance Association in Scotland).
What precautions should I take?
If you have ever had anaphylaxis you must be referred to an allergy
clinic for full assessment and to identify the cause of the reaction.
If you or someone you know is prone to anaphylaxis, the following
precautions should be taken to prevent future anaphylactic reactions:
Have your own preloaded adrenaline auto-injector
Carry your medicines with you at all times and make sure
you're familiar with how to use them
Inform other people at home, work or college about your
allergy and where you keep your medicines and how they're
Make sure that your medication is easily accessible and check
its 'use-by' date regularly
Wear a special medic alert bracelet or necklace that will inform
emergency medical staff about your condition