Anaphylaxis: assessment and referral after emergency treatment

Consultation with topic experts

We consulted with TEs about the proposal to replace the NICE guideline recommendations about post-anaphylaxis observation periods for people 16 years or older with the RCUK's recommendations, and about the wording of the proposed recommendations. We provided TEs with draft wording adapted from the table on page 43 of the RCUK's Emergency treatment of anaphylaxis. We had responses from 9 TEs that included: a GP with an extended role in allergic medicine; a matron with an extended role in emergency and acute medicine; a nurse adviser and health visitor; a consultant in paediatric emergency medicine; a consultant nurse in adult immunology and allergy; a consultant paediatrician; a consultant paediatric allergist; 2 consultants in emergency medicine; and a professor of paediatric allergy.

Eight of 9 respondents agreed with the proposal to replace NICE's recommendation about people aged over 16 years with the RCUK's recommendations. TEs commented that the proposal made practical sense and would ensure clarity. They commented that the RCUK's guidelines are robust, evidence-based, and that there is a good clinical rationale for stratifying observation period durations according to risk. One TE noted that the proposal would address a current gap in NICE's guideline about observing people who are at increased risk for longer than 12 hours. One TE did not disagree per se but had concerns that the proposed amendment fails to adequately highlight the information needs for safe discharge as per section 8.3 of the RCUK guidance. The latter includes a bulleted list of recommendations taken from NICE's guideline about steps to take before discharge, so is assessed as being largely consistent with NICE's guideline.

However, 2 other TEs also commented that the draft wording provided would benefit from the addition of wording that recommends that a patient should be assessed by a senior clinician before a decision is made about length of observation period, further treatment and discharge. One TE commented that this was particularly important if fast track discharge is being considered for people who required 2 doses of adrenaline, but who have had a successful (negative) allergy challenge test. We will therefore amend the draft wording to ensure that it recommends that a patient should be reviewed by a suitably qualified and experienced clinician before a decision about length of observation period and discharge is made.

Another TE commented that the wording 'in some circumstances, it may be reasonable for some patients to be discharged after 2 hours despite needing 2 doses of intramuscular adrenaline, for example, following a supervised allergy challenge' has the potential to lead to wrong decisions. They commented that it should be modified to clarify that this is only the case if the other requirements for fast track discharge are met and the patient has been subject to senior review prior to discharge. We will amend the draft wording to reflect these comments and ensure clarity.

We asked TEs if they agreed with the proposal to retain the existing recommendation about observation periods for children; 5 agreed, 3 disagreed, and 1 was unable to comment on the treatment of children. The 3 who disagreed commented that the RCUK makes no distinction between the approach to the discharge of adults versus younger children. They commented that a risk-stratified approach would be of great benefit to low-risk children and their families, as well as to busy paediatric emergency departments who are seeing increasing anaphylaxis admissions. This comment is backed up by evidence provided by another TE.

The second TE noted there is no evidence to suggest children should be treated differently; another TE noted that it makes little sense to amend guidance for adults and not for children as the increase in cases is being driven 'almost wholly' by children. They noted that children are at lower risk of biphasic reactions (BRs) and provided new evidence (Dribin et al. 2025, see impact assessment in evidence provided by topic experts) that suggests for most children treated for anaphylaxis without cardiac involvement a 2-hour observation window is appropriate.

The TEs who agreed with our proposal to not use a risk-based approach with children emphasised that children may not be able to verbalise the signs of BRs. They noted that longer observation periods will allow time to check on children's carers' knowledge of anaphylaxis management. This issue is covered by NICE's guideline recommendations about discharging patients which includes a recommendation about educating parents and carers of children treated for anaphylaxis. One TE highlighted that some paediatric departments already have short stay observation units and suggested the wording could be amended to reflect this.

Budget impact and economic considerations

Recommending a stratified approach to post-anaphylaxis observation periods should act to reduce resource as evidence suggests the majority of people would be discharged after shorter observation times.

System impact

There are system benefits of having consistent and complimentary recommendations between NICE's guideline and the RCUK's guideline. The current inconsistency between 2 respected recommendation producing centres may result in confusion and uncertainty in the system.

Population impact

BMJ Best Practice describes anaphylaxis as a severe, generalised or systemic hypersensitivity reaction, characterised by rapidly developing life-threatening airway and/or breathing and/or circulation problems usually associated with skin and mucosal changes. The lifetime prevalence of anaphylaxis is estimated at approximately 1 in 1,333 people.

The prevalence of BRs is estimated at about 5% of anaphylaxis cases. The RCUK suggest fatality from BRs is 'very rare' and quote data from the European anaphylaxis registry from 2011 to 2019 (Kraft et al. 2020). This reports that 9,000 cases of anaphylaxis resulted in 28 deaths of which none were attributable to the 435 BRs recorded.