Anaphylaxis

Anaphylaxis is a severe, rapid-onset allergic reaction that can affect breathing and circulation, and is potentially fatal without immediate treatment. It is a medical emergency requiring urgent recognition and response.

• Sudden onset of hives, itching, or widespread skin flushing
• Swelling of the lips, face, tongue, or throat
• Difficulty breathing, wheeze, or a feeling of throat tightness
• Rapid heart rate and a sudden drop in blood pressure, causing dizziness or collapse
• Nausea, vomiting, or abdominal pain may also occur

• Triggered by an allergic reaction to a specific substance, most commonly certain foods, insect stings, or medicines (including some antibiotics).
• Occurs when the immune system releases a large amount of chemicals (such as histamine) in response to a trigger the person has previously been sensitised to.
• Risk is higher in people with known severe allergies or a previous history of anaphylaxis.

• Diagnosed clinically and immediately, based on the rapid onset of skin, breathing, and circulatory symptoms after exposure to a possible trigger — treatment should never be delayed to confirm the diagnosis with testing.
• A history of exposure to a known or suspected allergen shortly before symptom onset strongly supports the diagnosis.

Anaphylaxis is a medical emergency. Intramuscular adrenaline (epinephrine), given into the outer thigh, is the first-line, life-saving treatment and should be given immediately without waiting for other measures.

The patient should be positioned lying flat with legs raised (or sitting up if breathing is severely difficult), and oxygen given if available.

A second dose of adrenaline may be repeated after 5–15 minutes if there is no improvement.

Intravenous fluids are given for low blood pressure, and additional medicines such as an antihistamine or corticosteroid may be given to support recovery, though these are not substitutes for adrenaline.

Anyone who has had anaphylaxis needs urgent transfer to hospital for observation, as symptoms can recur several hours after the initial reaction.

• Identify and strictly avoid any known trigger, such as a specific food, medicine, or insect sting.
• People with known severe allergies should carry an adrenaline auto-injector where available and know how to use it.
• Inform healthcare workers of any known drug allergies before receiving treatment.
• Wear a medical alert bracelet or carry written information about severe allergies where possible.