20th March 2024

Anaphylaxis

Anaphylaxis is a systemic IgE-mediated hypersensitivity reaction which results in life-threatening airway and circulatory problems after exposure to an allergen. It is caused by release of inflammatory mediators after degranulation of basophils and mast cells. The initial management is IM adrenaline and in adults the concentration is 1mg/mL (1:1000) concentration. The intramuscular dose of adrenaline is 500 micrograms (0.5mL).  Anaphylactic reactions may be confirmed by measuring mast cell tryptase levels. Ideally, three samples should be taken. These should be taken as soon as feasible after suspected anaphylaxis (but do not delay treatment to measure tryptase levels), 1–2 hours (but no later than 4 h) after onset of symptoms and at least 24 hours after complete resolution or in convalescence.