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Anaphylaxis and anaphylactic shock

What is anaphylaxis?

Anaphylaxis is a potentially life-threatening, severe allergic reaction characterised by swelling of the mouth and throat, hives and a feeling of impending doom.

It develops suddenly, usually within minutes of contact with the trigger substance, or allergen, and gets worse quickly. However, in some people symptoms may not appear until up to an hour later.

What causes anaphylaxis?

An anaphylactic reaction occurs when the immune system creates specific disease-fighting antibodies (called immunoglobulin E or IgE) towards a trigger substance that is normally harmless, such as food. When you are first exposed to the substance, your body does not react, but it does produce the IgE antibodies. When you are exposed to the trigger again, the antibodies spring into action, releasing large amounts of a protein called histamine. The histamine protein causes the anaphylactic reaction.

What is anaphylactic shock?

Severe cases of anaphylaxis can result in anaphylactic shock, which results in difficulty breathing, a weak but rapid pulse and sudden drop in blood pressure. If anaphylactic shock isn't treated immediately, it can result in unconsciousness, coma and ultimately death.

Signs and symptoms of anaphylaxis

The immediate signs and symptoms of anaphylaxis include:

  • Severe itching of the eyes, face, or skin
  • Facial swelling
  • Swelling of tongue or throat
  • Swallowing and breathing difficulties
  • Abdominal pain
  • Cramps
  • Vomiting
  • Diarrhoea
  • Urticaria (hives)
  • Angioedema (swelling underneath the skin).

A severe allergic reaction can quickly progress to anaphylactic shock resulting in an increased heart rate, sudden weakness, a drop in blood pressure, shock, and ultimately, unconsciousness, coma and death.

In case of emergency

If you, or someone around you, is experiencing the symptoms of anaphylaxis:

  • Seek emergency medical attention immediately
  • Call 999 for an ambulance
  • Lie the person down flat on their back if they are not unconscious, having breathing difficulties or pregnant
  • Use an adrenaline auto-injector on the person if there is one available. Give a second injection 5-15 minutes later if they have one and symptoms are still evident.

Common triggers of anaphylaxis

Common triggers that can cause anaphylaxis and anaphylactic shock include:

  • Food - generally the most common cause of anaphylaxis. Common food triggers include peanuts, tree nuts (cashews, pecans, almonds, walnuts), shellfish (prawns, lobster, crab), fish, dairy products for those with milk allergies, egg whites, wheat (more common in children) and sesame seeds.
  • Insect stings and bites - the venom from insect stings and bites from bees, wasps and hornets can cause anaphylactic onset. If possible, remove the stinger immediately.
  • Medications - especially penicillin, but also ibuprofen, naproxen, aspirin and other NSAIDs.
  • Latex - products made from natural rubber latex, including some gloves used in medical and dental practices and some condoms.
  • Anaesthesia- both local and general anaesthetics used in operations and medical procedures, although this is rare.
  • Contrast agents - a rare reaction to the special dyes used in some tests to help areas of your body show up better on scans.
  • Exercise- although less common, intense aerobic exercise can trigger anaphylaxis in some people. This usually occurs in extreme cold or warm temperatures or after eating an allergy provoking food.

Pollens and other inhaled allergens can, but rarely do, cause anaphylaxis.

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