What is anaphylaxis?

Anaphylaxis is a severe and often sudden allergic reaction. It can occur when a person with allergies is exposed to something they are allergic to (known as an allergen). Reactions usually begin within minutes of exposure and progress rapidly, but can occur up to 2-3 hours later. It is potentially life-threatening, and always requires an immediate emergency response.

What can cause anaphylaxis?

Common allergens that can trigger anaphylaxis are:

  • foods (e.g. peanuts, tree nuts, milk/dairy foods, egg, wheat, fish/seafood, sesame and soya)
  • insect stings (e.g. bee, wasp)
  • medicines (e.g. antibiotics, pain relief such as ibuprofen)
  • latex (e.g. rubber gloves, balloons, swimming caps).

It is very unusual for someone with food allergies to experience anaphylaxis without actually eating the food: skin contact with an allergen is very unlikely to trigger anaphylaxis (but can cause contamination if handling food, which if eaten can then trigger a reaction).

The time it takes for a reaction to turn into a severe life-threatening reaction varies, depending on the allergen:

  • Food: symptoms often begin immediately and may be mild, initially. Severe reactions can occur within minutes, but often develop over 30 minutes or so after exposure. Occasionally, severe reactions happen over 1-2 hours after eating: this has been reported especially for reactions to milk. Such reactions can mimic a severe asthma attack, without any other symptoms (e.g. skin rash) being present.
  • Insect stings: severe reactions are often faster, occurring within 10-15 minutes.

What are the symptoms of anaphylaxis?

Anaphylaxis usually develops suddenly, and gets worse very quickly. Symptoms include:

  • AIRWAY:
    Persistent cough, vocal changes (hoarse voice)
    Difficulty in swallowing, swollen tongue
  • BREATHING:
    Difficult or noisy breathing
    Wheezing (like an asthma attack)
  • CONSCIOUSNESS:
    Feeling lightheaded, dizzy or faint.
    Clammy skin.
    Confusion and severe anxiety.
    Sudden drop in level of consciousness (due to a drop in blood pressure)

Usually, there are also other, more mild allergy symptoms, such as an itchy, raised rash (hives), feeling or being sick, lip / face swelling, or stomach pain. However, in some cases, this does not occur, and the first symptoms seen are those of a severe reaction.

Why does anaphylaxis occur?

An allergic reaction occurs because the body’s immune system reacts to a substance that it wrongly perceives as a threat. The body produces an “allergy” antibody called Immunoglobulin E (IgE), which sticks to the substance (“allergen”) and causes the release of chemicals such as histamine. In the skin, this results in an itchy rash, swelling and flushing.

Many children (not just those with asthma) can develop breathing problems during an allergic reaction, similar to an asthma attack. The throat can tighten, causing swallowing difficulties and a high-pitched noise (stridor) on breathing.

How is anaphylaxis treated?

In severe cases, the allergic reaction can progress within minutes into a life-threatening reaction. The treatment of anaphylaxis is to give adrenaline, by an injection into the outer muscle of the mid-thigh (upper leg). Adrenaline treats both the symptoms of the reaction, and can also stop it from becoming worse. Other “allergy” medicines (such as antihistamines) can help with mild symptoms, but are not effective for severe reactions (anaphylaxis).

Administration of adrenaline can be lifesaving. Some anaphylaxis reactions require more than a single dose of adrenaline; children can initially improve but then deteriorate later. It is therefore vital to always dial 999 and request an ambulance whenever anaphylaxis has occurred – even if there has been a good response to an adrenaline injection.

Outside hospital, adrenaline can be safely given by non-healthcare workers as an injection into the muscle using an adrenaline auto-injector (AAI)[PJT1] . Current brands available in the UK are EpiPen®, Emerade®, Jext®. This can be life-saving.

Delays in giving adrenaline are a common finding in fatal reactions.

Giving adrenaline can be lifesaving, and should be administered at the first signs of anaphylaxis. IF IN DOUBT, give adrenaline.