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What is anaphylaxis

Anaphylaxis is a severe and often sudden allergic reaction, which is potentially a life-threatening condition. It occurs when an individual comes into contact with an allergen. Common allergens include, dust, pollen and pet hair, vaccines can cause anaphylactic reactions and has the potential to be fatal, however, this is very rare.

In an anaphylactic reaction, histamine is secreted throughout the body, this caused vasodilation, lowering blood pressure and smooth muscle constriction that leads to airway constriction and gastrointestinal symptoms, such as vomiting, abdominal cramps and diarrhoea.

If your patient is exposed to something, they are allergic to, reactions tend to be within minutes and progress rapidly. Which is why you normally ask patients to consent to staying at your clinic for ten minutes following vaccination.

When recognising and treating any acutely ill patient it is important to take the ABCDE approach.

The key principle of this assessment is to complete an initial assessment, to reassess the patient regularly and to identify and treat any problems.

A (Airway) Airway swelling in throat and or tongue:

  • The patient has difficulty breathing and swallowing and feels that the throat is closing
  • Hoarse voice
  • The patient has difficulty breathing and swallowing and feels that the throat is closing
  • Hoarse voice
  • Stridor – high pitched inspiratory noise caused by upper airway obstruction

B (Breathing) Shortness of breath – increased respiratory rate:

  • Stridor or wheeze
  • Patient becomes tired
  • Confusion caused by hypoxia
  • Cyanosis (blue tinging) but is usually a late sign
  • Respiratory arrest

C (Circulation) Signs of shock – pale, clammy:

  • Increased pulse rate (tachycardia)
  • Low blood pressure (if monitoring), feeling faint or dizzy that may lead to collapse
  • Decreased conscious level or loss of consciousness
  • Cardiac arrest

D (Disability) Unconsciousness or reducing levels of consciousness:

  • Confuse, aggressive
  • Look at the pupils do they react to light, are they equal in size?
  • Use the AVPU method to assess conscious level
  • A (Alert) are they alert?
  • V (Voice) do they respond to vocal stimuli?
  • P (Pain) do they respond to gently tapping their shoulders?
  • U (Unresponsive) or are they unresponsive to all stimuli?

E (Exposure) Respect and maintain the patient’s dignity:

  • Skin and mucosal changes are likely to be the first identifiable feature and is present in over 80% of anaphylactic reactions
  • These changes can be subtle or dramatic, it could include, just the skin, just mucosa or both
  • There may be erythema – patchy, or generalised red rash
  • Urticaria may be present (also called hives, nettle rash, weals or welks) and can appear anywhere on the body.
  • The welks may be pale, pink or red and may look like nettle stings
  • They can be different shapes and sizes and often surrounded by a red flare
  • They tend to be itchy

To treat Anaphylaxis

  • Phone 999
  • Administer IM Adrenaline
  • Position patient as per their symptoms

Adrenaline causes vasoconstriction (constricts the blood vessels which increases the blood pressure) and bronchodilation (which dilates the bronchioles and bronchi, which increases airflow to the lungs making it easier for the individual to breathe).

Adrenaline works best if it is given early after the onset of the reaction and should be given to all patients that are displaying life threatening features.

The dose of adrenaline to be administered IM doses of 1:1000 adrenaline

Children over 12 and adults                         500mcg (0.5 ml)

Child 6-12                                                            300 mcg (0.3ml)

Child less than 6                                                150 mcg (0.15ml)

When using an ampoule to draw up the adrenaline required dose, a blue 25mm needle is suitable for all ages, a green 38mm should be used for very large adults. Remember there is no need to change the needle for administration after drawing up the adrenaline. The preferred site of injection is the midpoint of the thigh, anterolateral aspect. As you are administering with a normal needle, the skin will need to be exposed in order to administer to the muscle of the individual, it will not work through the clothes. Only adrenaline auto-injectors can be administered through clothing.

Anaphylaxis, adrenaline administration and BLS are covered on our vaccination courses, to book your place, please go to

Written by Lisa Humble (ECG Clinical Development Manager), Thursday 17th September 2020