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
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.
Watch our video - Allergic reactions
What to look for - Allergic reactions
These are the six key things to look for:
- Difficulty breathing (e.g. tight chest and wheezing)
- Swelling of the tongue and throat
- Itchy or puffy eyes
- An outbreak of blotchy skin
- Signs of shock
What you need to do - Allergic reactions
• 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 straight away. Tell them you think
someone is having a severe allergic reaction and give any
information you have on what may have triggered it (e.g. 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
• Help them into a comfortable sitting position, leaning
forward slightly, to help their breathing.
• If they become unconscious, open their airway and check
breathing. Follow the instructions for treating someone who is