Anaphylaxis is a severe, systemic, and potentially life-threatening allergic reaction.
It is characterised by its rapid onset—often occurring within seconds or minutes of exposure to an allergen—and a swift progression of symptoms that can lead to a medical emergency if not treated immediately.
Understanding how to recognize the signs and administer the correct treatment is vital for anyone living with severe allergies or caring for those who do.
Anaphylaxis affects multiple systems in the body simultaneously. While some people may experience mild skin irritation first, others may progress directly to respiratory or circulatory distress.
1. Skin and Mucosal Changes
Flushing: A sudden reddening of the face, neck, or chest.
Urticaria (Hives): Itchy, raised red welts or a “nettle rash” appearing across the body.
Angioedema: Significant swelling, most commonly seen in the lips, tongue, or around the eyes.
2. Respiratory Distress
Shortness of Breath (Dyspnoea): Difficulty catching one’s breath or rapid breathing.
Wheezing and Chest Tightness: A high-pitched whistling sound caused by narrowing airways.
Stridor: A harsh, vibrating noise when breathing in, indicating a blocked upper airway.
Respiratory Arrest: The complete cessation of breathing.
3. Cardiovascular and Circulatory Issues
Tachycardia: A dangerously fast heart rate as the body tries to maintain blood pressure.
Bradycardia: A slow heart rate, often seen in the late stages of a severe reaction.
Hypotension: A sudden drop in blood pressure, leading to “anaphylactic shock,” dizziness, or loss of consciousness.
Anaphylaxis occurs when the immune system overreacts to a substance it perceives as a threat.
Common Triggers
Food Products: Most notably peanuts, tree nuts, shellfish, milk, eggs, and sesame.
Medications: Certain antibiotics (like Penicillin), non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin, or general anaesthetics.
Insect Stings: Particularly wasps and bees.
Latex: Often found in medical gloves, balloons, or certain types of elastic.
Exercise: In rare cases, physical activity can trigger a reaction, sometimes specifically after consuming certain foods (exercise-induced anaphylaxis).
Known Risk Factors
Certain underlying conditions can increase both the likelihood and the severity of a reaction. A helpful way to remember the primary risk factors is the “Triple A” rule:
Allergies (Pre-existing sensitivities).
Asthma (Poorly controlled asthma significantly increases the risk of fatal anaphylaxis).
Atopic Dermatitis (Eczema).
Other risks include pre-existing Cardiovascular Disease (CVD) and a history of previous anaphylactic reactions, which may indicate that future reactions will be more severe.
Adrenaline (Epinephrine) is the first-line treatment for anaphylaxis. It acts quickly to reverse the physiological processes that cause life-threatening symptoms.
For Adults and Children (Over 12 Years)
The standard emergency protocol involves:
Dosage: 500 micrograms (0.5 mL) of 1:1000 Adrenaline IM (repeat after 5 min if no better)
Administration: Given via Intramuscular (IM) injection into the outer mid-thigh. The muscle in the thigh is highly vascularised, allowing the medication to enter the bloodstream rapidly.
Follow-up: If there is no clinical improvement or if symptoms worsen after 5 minutes, a second dose of IM Adrenaline should be administered.
Why is Adrenaline Effective?
Adrenaline works by targeting specific receptors in the body to stabilize the patient:
Airway Protection: It reduces mucosal oedema (swelling), preventing the throat from closing.
Respiratory Relief: It acts as a bronchodilator, relaxing the muscles in the lungs to open the airways.
Cardiac Support: Its powerful inotropic (strength of contraction) and chronotropic (heart rate) effects help raise blood pressure and counteract the effects of shock.
Anaphylaxis is a medical emergency that requires a calm, fast response. Always call emergency services immediately if you suspect a reaction is occurring, even if Adrenaline has been administered, as “rebound” (biphasic) reactions can occur several hours later.
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