NICE vs BSACI: Management of Anaphylaxis (2025) - A Clinical Comparison
Anaphylaxis is a medical emergency requiring immediate, standardised management. In the UK, clinicians primarily refer to guidelines from the National Institute for Health and Care Excellence (NICE) and the British Society for Allergy & Clinical Immunology (BSACI). While aligned on core principles, key differences in their approach can influence clinical practice. This comparison focuses on the 2020 NICE guideline (NG129) and the 2021 BSACI guideline, which remain the current standards in 2025.
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Diagnosis and Assessment
The cornerstone of both guidelines is the prompt recognition of anaphylaxis. They agree that anaphylaxis is likely when there is sudden onset and rapid progression of symptoms, but they offer different diagnostic criteria.
NICE Approach
- Criteria-Based: NICE uses a specific set of criteria. Suspect anaphylaxis when all three of the following are present:
- Sudden onset and rapid progression of symptoms.
- Life-threatening Airway, Breathing, or Circulation problems (e.g., airway swelling, stridor, hypoxia, hypotension, collapse).
- Skin and/or mucosal changes (e.g., flushing, urticaria, angioedema).
- Key Point: NICE explicitly states that skin or mucosal changes alone are not a sign of an anaphylactic reaction. Skin changes may be absent in up to 20% of cases ("biphasic" reactions are a known risk).
BSACI Approach
- Symptom-Based (Clinical Judgement): BSACI provides a broader, more inclusive definition. It suggests anaphylaxis is highly likely when there is a sudden onset and rapid progression of symptoms with involvement of the airway, breathing, and/or circulation.
- Key Point: Unlike NICE, BSACI does not mandate the presence of skin/mucosal changes for diagnosis. It emphasises clinical judgement, particularly for reactions involving two or more body systems rapidly. This may lead to a lower threshold for diagnosis, especially in cases of cardiovascular collapse without skin manifestations.
Practical Takeaway: The NICE criteria are more structured and specific, potentially reducing over-diagnosis. The BSACI approach prioritises clinical suspicion and may capture more atypical presentations. Clinicians should be aware of both to avoid missing a diagnosis due to the absence of skin signs.
Acute Treatment and Management
Both guidelines are in complete agreement on the primary, life-saving treatment: Intramuscular (IM) Adrenaline is the first-line and most important treatment. The recommended site is the anterolateral aspect of the middle third of the thigh.
Key Alignment
- Adrenaline (Epinephrine) 1:1000: 500 micrograms IM (0.5 mL) for adults and children >12 years (or >50 kg). Doses for children are weight-based.
- Repeat Doses: Can be given every 5 minutes if there is no improvement.
- Positioning: Lie the patient flat with legs raised (or in a position of comfort if breathing is difficult). Do not allow the patient to sit or stand.
- Call for Help / 999: After administering adrenaline.
Subtle Differences in Adjuncts
- Fluid Resuscitation: Both recommend IV fluids for hypotension not responding to adrenaline. BSACI provides more detailed guidance on rapid volume expansion (e.g., 20 mL/kg crystalloid bolus in children, 500 mL bolus in adults), which is consistent with resuscitation council guidelines.
- Antihistamines and Corticosteroids: Both guidelines relegate these to a secondary role. NICE is more explicit in stating they should not be used as first-line treatment for anaphylaxis, as they do not treat airway obstruction or shock. They may be considered for relief of persistent skin symptoms but only after adrenaline has been given.
Practical Takeaway: The treatment algorithm is nearly identical. The critical message is "Adrenaline First, Adrenaline Fast." Do not delay adrenaline administration to give antihistamines or steroids.
Special Situations and Follow-up
Biphasic Reactions and Observation
- NICE: Recommends observing adults for 6-12 hours after a reaction, depending on clinical features (e.g., severity, response to treatment, asthma). For children, observe for a minimum of 6-12 hours in a specialist paediatric setting.
- BSACI: Also recommends observation for 6-12 hours, aligning with NICE. It provides a nuanced discussion on risk factors for biphasic reactions.
Difference: The guidelines are similar, but NICE provides more structured timeframes linked to specific risk assessments.
Discharge and Prescription of Adrenaline Auto-Injectors (AAIs)
- Both guidelines agree that all patients who have had a suspected anaphylactic reaction should be referred to a specialist allergy service.
- Key Difference in AAI Prescription:
- NICE: Recommends prescribing two AAIs before discharge for all patients at risk of future anaphylaxis.
- BSACI: Also recommends two AAIs, but provides a more detailed rationale, including the need for a spare device (e.g., for home and school/work) and the potential for a first dose to misfire or be insufficient.
- Patient Education: BSACI places a stronger emphasis on the absolute necessity of comprehensive, structured training on AAI use and anaphylaxis management plan provision at discharge.
Practical Clinical Flow
A consolidated, practical flow for the UK clinician based on both guidelines:
- Suspect Anaphylaxis: Use a low threshold, especially with rapid-onset airway/breathing/circulation problems (BSACI) or the specific triad of symptoms (NICE).
- Immediate Action: Lie flat, legs raised. Call for senior help/ cardiac arrest team/ 999.
- First-line Treatment: IM Adrenaline into the anterolateral thigh. Do not hesitate.
- Second-line (if IV/IO access available): If hypotensive and not responding to IM adrenaline, initiate IV fluid resuscitation.
- Oxygen & Monitoring: Give high-flow oxygen. Monitor SpO2, ECG, blood pressure.
- Reassess & Repeat: If no improvement after 5 minutes, repeat IM adrenaline.
- Post-stabilisation: Observe for 6-12 hours. Refer to Allergy Clinic. Prescribe two AAIs and provide verifiable training on their use. Provide a written Anaphylaxis Management Plan.
Frequently Asked Questions (FAQs)
1. Which guideline should I follow in an emergency?
Answer: In the acute setting, the treatment principles are identical. Follow the Resuscitation Council (UK) algorithm, which is entirely consistent with both NICE and BSACI. For diagnosis, be aware that BSACI's criteria may be more sensitive for atypical presentations.
2. What if the patient has symptoms but doesn't meet the strict NICE criteria?
Answer: Err on the side of caution. The BSACI approach validates treating based on strong clinical suspicion, even if skin signs are absent. The risk of under-treating anaphylaxis far outweighs the risk of an unnecessary dose of IM adrenaline.
3. How many adrenaline auto-injectors should be prescribed at discharge?
Answer: Both guidelines recommend two devices. This is now considered standard of care in the UK to ensure a backup is available.
4. Are antihistamines completely useless in anaphylaxis?
Answer: They are useless for the life-threatening features (airway obstruction, shock). NICE is particularly strong on this point. They can be considered later for residual urticaria, but must never delay or replace adrenaline administration.
5. Who needs a referral to an allergy specialist?
Answer: All patients with a suspected anaphylactic reaction should be referred. This is a key point of agreement to identify the trigger, provide avoidance advice, and ensure long-term management.
Source Links
- NICE Guideline NG129 (2020): Anaphylaxis: assessment and referral after emergency treatment. NICE NG129
- BSACI Guideline (2021): Anaphylaxis: Summary of guidelines. BSACI anaphylaxis guidance
- Resuscitation Council (UK): Emergency treatment of anaphylaxis guidelines. Resuscitation Council UK: anaphylaxis guideline