Allergies and anaphalaxis


An allergy is a reaction the body has to a particular food or substance.

Half of all children in the UK have allergies. When an allergy occurs it is a learning curve in understanding what to avoid and how to control and manage the allergy.

Having an allergy can be a nuisance and affect your everyday activities, but most allergic reactions are mild and can be largely kept under control.

Severe reactions can occasionally occur, but these are uncommon.

Substances that cause allergic reactions are called allergens. 

The more common allergens include:    

  • grass and tree pollen – an allergy to these is known as hay fever (allergic rhinitis)
  • dust mites
  • animal dander, tiny flakes of skin or hair
  • food – particularly nuts, fruit, shellfish, eggs and cows' milk
  • insect bites and stings
  • medicines – including ibuprofen, aspirin and certain antibiotics
  • latex – used to make some gloves and condoms
  • mould – these can release small particles into the air that you can breathe in
  • household chemicals – including those in detergents and hair dyes

Most of these allergens are generally harmless to people who are not allergic to them.

Most allergic reactions are mild, but occasionally a severe reaction called anaphylaxis or anaphylactic shock can occur.

This is a medical emergency and needs urgent treatment.

Common symptoms of an allergic reaction include:

The symptoms vary depending on what you're allergic to and how you come into contact with it. For example, you may have a runny nose if exposed to pollen, develop a rash if you have a skin allergy, or feel sick if you eat something you're allergic to.

In many cases, the most effective way of managing an allergy is to avoid the allergen that causes the reaction whenever possible. For example, if you have a food allergy, you should check a food's ingredients list for allergens before eating it.

There are also several medicines available to help control symptoms of allergic reactions, including:

  • antihistamines – these can be taken when you notice the symptoms of a reaction, or before being exposed to an allergen, to stop a reaction occurring

  • decongestants – tablets, capsules, nasal sprays or liquids that can be used as a short-term treatment for a blocked nose

  • lotions and creams, such as moisturising creams (emollients) – these can reduce skin redness and itchiness

  • steroid medicines – sprays, drops, creams, inhalers and tablets that can help reduce redness and swelling caused by an allergic reaction

The best way to prevent an allergic reaction is to avoid the substance that you're allergic to, although this is not always easy or practical.

Practical advice to help avoid the most common allergens can be found here


A reaction produced by the body's immune system when exposed to a normally harmless substance.


The exaggeration of the normal effects of a substance. For example, the caffeine in a cup of coffee may cause extreme symptoms, such as palpitations and trembling.


Where a substance causes unpleasant symptoms, such as diarrhoea, but does not involve the immune system.
People with an intolerance to certain foods can typically eat a small amount without having any problems.
Very occasionally, a severe reaction called anaphylaxis can occur.


Anaphylaxis is a severe and potentially life-threatening reaction to a trigger such as an allergy.

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.

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

Make sure your tell your school if you have anaphylaxis

  • If you need one, make sure that you have an in date Epipen on you and that you give your school a spare Epipen to be kept at school
  • Make sure that school staff are aware that you are at risk of an anaphylactic reaction to certain triggers. Your school nurse will discuss a care plan with you, your parents or carer and the school to make sure that the correct procedure is followed if necessary. It’s a good idea to tell your friends and classmates too.

Anaphylaxis is the result of the immune system, the body's natural defence system, overreacting to a trigger.

This is often something you're allergic to, but not always.

Common anaphylaxis triggers include:

Anaphylaxis usually develops suddenly and gets worse very quickly.

The symptoms include:

There may also be other allergy symptoms, including an itchy, raised rash (hives); feeling or being sick; swelling (angioedema) or stomach pain. These symptoms can also occur on their own, without the more severe ones. Where that is the case, the reaction is likely to be less serious but you should watch carefully in case any of the more severe ones develop.

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 aeroallergen symptoms, such as hay fever
  • During times of emotional stress
  • If you have been drinking alcohol.

If you or someone you know is having a severe allergic reaction, it is vital to receive an adrenaline injection. If they have their own adrenaline, this must be given as soon as a severe reaction is suspected to be occurring and an ambulance must be called immediately. 

Practical points to follow if you are helping someone else, and to make sure your friends know what to do if you have an allergic reaction:

  • Try to make sure that the person suffering an allergic reaction remains as still as possible
  • Preferably they should be lying down and if they are feeling weak, dizzy or appear pale and sweating their legs should be raised
  • When dialling 999, say that the person is suffering from anaphylaxis (anna-fill-axis)
  • Give clear and precise directions to the emergency operator, including the postcode of your location
  • If adrenaline has been given, make a note of the time this was administered. A second dose can be given after five minutes if there has been no improvement
  • If the person’s condition deteriorates after making the initial 999 call, a second call to the emergency services should be made to ensure an ambulance has been dispatched
  • Send someone outside to direct the ambulance crew when they arrive
  • Try to ascertain what food or substance may have caused the reaction and ensure the ambulance crew knows this.

Read about how to treat anaphylaxis for more advice about using auto-injectors and correct positioning.

If you have a serious allergy or have experienced anaphylaxis before, it's important to try to prevent future episodes.

The following can help reduce your risk:

  • identify any triggers – you may be referred to an allergy clinic for allergy tests to check for anything that could trigger anaphylaxis
  • avoid triggers whenever possible – for example, be careful when food shopping or eating out if you have a food allergy
  • carry 2 in-date adrenaline auto-injectors at all times – give yourself an injection whenever you think you may be experiencing anaphylaxis, even if you're not completely sure

Read more about preventing anaphylaxis