Medical

Urticaria after food contact — distinguishing mild allergy from anaphylaxis

Foundation

Adult · 31yr · male

Patient Information

Dispatch	You are called urgently to a stall at an outdoor food festival where bystanders are shouting that a man is having a severe allergic reaction. A 31-year-old male (Jason Park) is sitting on a chair, looking uncomfortable. Several bystanders are crowding around him and one is waving an EpiPen shouting 'Give him this!'
Patient	Jason Park — 31yr (79kg)
Incident History	Patient ate a Thai food sample from one of the festival stalls approximately 15 minutes ago. Within 5 minutes he developed an itchy rash across his chest, arms, and neck. He has never had this before. He does not have a known nut allergy. No previous anaphylaxis. No history of asthma. The stall used peanut oil in cooking.
Emergency Contact	Min Park (Partner) — 0412 447 091

Initial Rapid Assessment

Response	Alert
Airway	Patent. Speaking clearly and easily in full sentences. No stridor. No muffled voice. No drooling. No swelling of the tongue or lips visible.
Breathing	Comfortable. RR 16. No wheeze. No increased work of breathing. SpO2 99% on room air.
Circulation	Radial pulse strong and regular. Skin — raised, blotchy, red urticarial welts across the chest, upper arms, and neck. No pallor. No diaphoresis. CRT <2s. BP 128/82.
Disability	GCS 15 (E4V5M6). Alert and orientated. Anxious — frightened by the bystanders' reaction. No dizziness or faintness. No confusion.
Exposure	Widespread urticaria (hives) across the chest, upper arms, neck, and upper back — raised, red, blotchy welts. Severely itchy. No angioedema to lips, tongue, or periorbital area. No visible rash on the face or scalp.

Vitals

Time	SpO2	Resp Dist	RR	Pulse	BP	CRT	GCS	PERL	Temp	BGL	Pain
Initial	99% (RA)	Nil	16	96	128/82	<2s	15	4 4 ++	37	–	2
30 mins	99% (RA)	Nil	16	86	124/80	<2s	15	4 4 ++	37	–	1

History Taking

Treatment Response

Diagnosis

Mild allergic reaction — cutaneous urticaria (hives) only, following likely peanut oil exposure in a non-anaphylactic pattern. This is NOT anaphylaxis. Key assessment points: airway is completely clear (no stridor, no swelling, no muffled voice); breathing is normal (no wheeze, SpO2 99%, RR 16, no distress); cardiovascular is normal (BP 128/82, HR 96 — mildly elevated from anxiety only, CRT normal). Treatment: Loratadine 10mg orally (non-sedating antihistamine) and observation for minimum 60 minutes. Urticaria alone, without any systemic features, does NOT warrant adrenaline. If at any point systemic features develop — throat tightness, stridor, wheeze, hypotension, vomiting, or loss of consciousness — escalate immediately to anaphylaxis protocol and administer adrenaline.

Facilitator Triggers — if trainees miss a critical step

! (If trainees administer adrenaline without any systemic features being present — facilitator stops the scenario. Facilitator note: adrenaline is a high-risk medication and is NOT indicated for urticaria alone without systemic anaphylaxis features. The appropriate treatment for cutaneous-only urticaria is an oral antihistamine and observation. Injecting adrenaline in this scenario is an error in clinical judgement.)
! (If trainees are pressured by the bystander waving the EpiPen and administer it — as above. Prompt BEFORE the action: 'Before you decide on treatment — what features of anaphylaxis are present? What is his airway like? His BP? His breathing?' Expected: trainee recognises no systemic features and declines to administer adrenaline.)
! (If trainees do not ask about throat tightness, wheeze, or systemic symptoms — prompt: 'He has the rash — but what other symptoms are you specifically looking for to determine severity?' Facilitator note: differentiating cutaneous allergy from anaphylaxis requires a systematic check of airway, breathing, and cardiovascular involvement.)
! (If trainees do not plan for observation — prompt after antihistamine given: 'You have given the antihistamine — what happens next?' Facilitator note: a minimum 60-minute observation period after an allergic reaction is important. Symptoms can recur or escalate. Do not discharge immediately after antihistamine.)
! (If any systemic feature develops during observation at 20 minutes — facilitate an escalation trigger: patient reports throat tightening. This converts the scenario to anaphylaxis management — the trainee must now administer adrenaline and call CSP.)

Treatment Objectives

1. Ensure scene safety — remove patient from the immediate vicinity of the food stall; reduce crowd of bystanders.
2. Don appropriate PPE — gloves.
3. Politely but firmly take control from bystanders — do NOT allow an EpiPen to be administered by a bystander before completing your assessment.
4. Perform Primary Survey — systematically assess airway, breathing, and circulation. Confirm: airway completely patent (no stridor, no swelling, no muffled voice); breathing comfortable (no wheeze, no distress, SpO2 99%); cardiovascular normal (BP 128/82, HR 96 — mildly elevated from anxiety only).
5. Document that NO systemic features of anaphylaxis are present at this time.
6. Conduct focused history — food consumed (peanut oil), prior allergic reactions (nil), prior anaphylaxis (nil), medications (nil), asthma (nil).
7. Complete Vital Sign Survey — all parameters normal apart from mildly elevated HR consistent with anxiety.
8. Inspect skin — document distribution of urticaria (chest, arms, neck, upper back). Confirm no angioedema to lips, tongue, or periorbital region.
9. Administer Loratadine 10mg orally — confirm patient can swallow and there is no throat swelling. Do NOT administer adrenaline in the absence of systemic features.
10. Observe for a minimum of 60 minutes — monitor for development of any systemic feature: throat tightness, stridor, wheeze, hypotension, vomiting, syncope, or rapidly spreading rash.
11. Reassess vital signs every 10–15 minutes during observation.
12. Reassure patient — explain clearly that his assessment shows a mild allergic reaction (skin only) and not anaphylaxis, and that you are giving him an antihistamine and observing him closely.
13. Advise patient: follow up with GP after the event; seek investigation for possible peanut allergy; consider carrying an antihistamine in the future; if he develops any throat tightness or breathing difficulty after discharge — call 000 immediately.
14. If any systemic feature develops during observation — escalate immediately: administer adrenaline IM, call CSP, place supine, monitor.
15. Scenario ends at 60-minute observation completion with symptom resolution and appropriate discharge advice.
16. Attention to hand hygiene will be given throughout the scenario.

Clinical references: Anaphylaxis · Loratadine · Primary Survey · Secondary & CNS Survey · Adrenaline

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Signs/Symptoms	Widespread itchy urticaria (hives) across chest, arms, and neck. No throat tightness. No difficulty breathing. No wheezing. No nausea, vomiting, or abdominal cramps. No dizziness or faintness. No swelling of lips or tongue. The itch is improving slightly since moving away from the stall.
Allergies	No known food allergies. No previous allergic reactions. No known latex or drug allergies. No asthma.
Medications	Nil regular medications.
Pertinent History	No prior allergic reactions. No prior anaphylaxis. No prior asthma. No eczema or hayfever. Has eaten Thai food before without reaction — unclear if that meal used peanut oil.
Last Oral Intake	The Thai food sample 15 minutes ago. Lunch approximately 2 hours prior — no unusual foods.
Events Leading	Patient was sampling food at the festival when he ate a Thai dish. The stall operator confirmed peanut oil was used in cooking. Within minutes, he developed the itchy rash. Bystanders became alarmed and called for EHS.
Treatment Prior	A bystander offered his EpiPen — patient declined. Nil other treatment given.

Onset	Approximately 5 minutes after eating a Thai food sample using peanut oil. Gradual onset over 2–3 minutes.
Pain	Itch is the primary symptom — 8/10 itchiness. Skin discomfort. No significant pain.
Quality	Intensely itchy, raised, red welts. Skin feels tight and tingly where the hives are present.
Radiates	Rash present across chest, upper arms, neck, upper back. Not extending to face or lower limbs.
Severity	Itch 8/10. Discomfort but not distress. No systemic symptoms.