Types of anaphylaxis

Types of Anaphylaxis: The Ways Severe Reactions Present

Anaphylaxis is one emergency with several recognised patterns, classified by trigger, by mechanism, and by how the episode unfolds, per NHS guidance on anaphylaxis.

By Trigger

• Food-induced: the commonest type in children - nuts, milk, egg, fish, shellfish, wheat, sesame
• Drug-induced: antibiotics, NSAIDs, anaesthetic agents, chemotherapy, contrast media
• Venom-induced: bee and wasp stings; a leading cause in adults
• Latex and other contact triggers
• Exercise-induced anaphylaxis: rare; exercise alone, or exercise within hours of eating a specific food (food-dependent, exercise-induced)
• Idiopathic: no trigger found despite thorough testing

By Mechanism

• IgE-mediated: the classic allergic pathway - prior sensitisation, then a full reaction on re-exposure
• Non-IgE-mediated (anaphylactoid): the same clinical picture triggered by direct mast-cell activation without allergy antibodies - certain drugs and contrast dyes act this way. The emergency treatment is identical

By Course

• Uniphasic: one wave of symptoms that resolves with treatment - the majority
• Biphasic: a second wave hours later without re-exposure (up to 1 in 5) - the reason for observation after the first wave
• Protracted: symptoms that persist or fluctuate for hours to days despite treatment - uncommon, managed in hospital

By Severity

Clinicians grade reactions from skin-only involvement through to life-threatening airway compromise and cardiovascular collapse. The grading matters for one practical reason: any involvement of breathing, throat, or circulation puts the episode in the severe category, whatever the skin looks like.

Frequently Asked Questions

Is anaphylactoid different from anaphylaxis? Clinically, no - same symptoms, same emergency treatment. The difference is the immune pathway, which matters later for testing, not in the moment.

What is exercise-induced anaphylaxis? A reaction triggered by physical exertion, sometimes only when exercise follows eating a particular food. Management includes avoiding the combination and carrying epinephrine.

Does the type change the emergency treatment? No. Every type of anaphylaxis gets the same first response: epinephrine and emergency services. Type matters afterwards, for prevention planning.

Can the same person have different types? Yes - someone with a nut allergy can also react to a drug. Each confirmed trigger goes into their action plan.