Dealing with an Allergic Reaction

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This leaflet is created from first aid advice provided by St John Ambulance, the nation's leading first aid charity. This advice is no substitute for first aid training - find a training course near you.

An allergy is the body's unexpected reaction to something it has come into contact with.

Something that triggers an allergic reaction is called an allergen.

One of the most common allergens is plant pollen, which often causes hay fever. Other allergens include: animal hair, insect stings, specific drugs, and foods - especially fruit, shellfish and nuts.

People develop allergies because their body's immune system mistakes the allergen for a threat, like an infection, and tries to fight it off.

A severe allergic reaction can develop within just a few seconds of the person coming into contact with the allergen. It can affect the whole body and, if not treated quickly enough, can potentially lead to death.

These are the six key things to look for:

  1. Difficulty breathing (eg tight chest and wheezing).
  2. Swelling of the tongue and throat.
  3. Itchy or puffy eyes.
  4. An outbreak of blotchy skin.
  5. Anxiety.
  6. Signs of shock.
  • If you notice these symptoms and you think someone is having an allergic reaction then you need to get emergency help to get them to hospital as fast as you can (even if the symptoms are mild or have stopped).
  • Dial 999 or 112 straightaway. Tell them you think someone is having a severe allergic reaction and give any information you have on what may have triggered it (eg an insect sting, or certain food, like peanuts).
  • If the person knows what their allergy is, they may have medication with them, like an auto-injector (for example EpiPen®, JEXT® or Emerade®). This is a pre-filled injection device, containing adrenaline/epinephrine, which when injected can help reduce the body's allergic reaction. Check if they have one, and if they do, help them to use it or do it yourself following the instructions.
  • Help them into a comfortable sitting position, leaning forward slightly, to help their breathing.
  • If they become unresponsive, open their airway and check breathing. Follow the instructions for treating someone who is unresponsive.

Note: these hints are no substitute for thorough knowledge of first aid. St John Ambulance holds first aid courses throughout the country.

Adapted from the St John Ambulance leaflet: allergic reactions. Copyright for this leaflet is with St John Ambulance.

Original Author:
St John Ambulance
Current Version:
Peer Reviewer:
St John Ambulance
Document ID:
28671 (v2)
Last Checked:
Next Review:
Now read about Anaphylaxis and its Treatment

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