Anaphylaxis 

• Multiple definitions exist
• Anaphylaxis is highly likely when any 1 of the following 3 criteria are fulfilled:

(1) Acute onset of an illness (minutes to several hours) with involvement of the skin, mucosal tissue, or both

• Localised to area of contact (eg perioral) or widespread generalized hives
• pruritus or flushing
• Angioedema/swollen lips-tongue-uvula

AND at least 1 of the following:

1. Respiratory compromise –  difficulty breathing, persistent coughing, tightness in throat. chest tightness, difficulty swallowing
   • Dyspnea
   • stridor
   • hypoxemia 
   • wheeze-bronchospasm
   • Hoarse voice

2. Reduced BP or associated symptoms of end-organ dysfunction
   • hypotonia [collapse]
   • syncope
   • incontinence

(2) Two or more of the following that occur rapidly after exposure to a likely allergen for that patient (minutes to several hours):

1. Involvement of the skin-mucosal tissue
   • Localised to area of contact (eg perioral) or widespread generalized hives
   • pruritus or flushing
   • Angioedema/swollen lips-tongue-uvula

2. Respiratory compromise
   • Dyspnea
   • wheeze-bronchospasm
   • stridor
   • reduced PEF
   • hypoxemia

3. Reduced BP or associated symptoms
   • hypotonia [collapse]
   • syncope
   • incontinence

4. persistent gastrointestinal symptoms
   • crampy abdominal pain
   • vomiting

(3) Reduced BP after exposure to known allergen for that patient (minutes to several hours):

• Infants and children:
  • low systolic BP (age specific) or 
  • greater than 30% decrease in systolic BP
• Adults:
  • systolic BP of less than 90 mm Hg or 
  • greater than 30% decrease from that person’s baseline

Assessment

• History
  • Timing of reaction in relation to food ingestion
  • Duration of symptoms
  • Exact foods eaten, how much and in what form (eg raw, cooked)
  • Other foods ingested at the time
  • Age when symptoms first occurred and frequency of occurrence
  • Reproducibility on repeat exposures
  • Details of previous treatment (eg antihistamines) and response

• Risk factors for development of IgE-mediated food allergy
  • Personal history of atopy (asthma, eczema or allergic rhinitis)
  • History of atopy or food allergy in parents or siblings
  • Known other IgE-mediated food allergies

Examination

• Acute presentation
  • Airway – hoarseness, stridor, tongue swelling, laryngeal oedema
  • Breathing – tachypnoea, cough, wheeze
  • Circulation – tachycardia, hypotension
  • Skin – rashes, urticaria and angioedema

Differential diagnosis

• Contact skin reaction
  • erythema and/or urticaria occurring on any areas of skin in contact with the food, more commonly around a child’s mouth. 
  • Common in children with eczema and not diagnostic of IgE-mediated food allergy
• Intercurrent illness
• Eczema
  • eczema alone is not indicative of an immediate IgE-mediated food allergy
• Food Protein Induced Enterocolitis Syndrome (FPIES)
  • profuse vomiting +/- diarrhoea occurring two to four hours after ingestion of a recently-introduced food. 
  • Sometimes associated with pallor, poor tone, a drop in body temperature and low blood pressure. 
  • FPIES is non-IgE mediated

Differential diagnosis of conditions that mimic anaphylaxis

• Tissue swelling
  • Idiopathic urticaria
  • Isolated angioedema
    • Idiopathic
    • Angiotensin-converting enzyme inhibitor-induced
    • Acquired or hereditary C1 esterase inhibitor deficiency
• Conditions mimicking upper airway oedema
  • Dystonic reactions mimicking symptoms of a swollen tongue
  • Acute oesophageal reflux (sudden onset of painful throat “swelling”)
• Flushing syndromes
  • Peptide-secreting tumours (eg, carcinoid syndrome, VIPomas)
  • Alcohol-related
  • Medullary carcinoma of thyroid
  • Red man syndrome (associated with vancomycin infusion)
• Neurological syndromes
  • Epileptic seizure
  • Stroke
• Other causes of collapse
  • Vasovagal episodes
  • Systemic inflammatory response syndrome
  • Shock due to other causes
• Acute respiratory distress
  • Asthma
  • Panic disorders
  • Globus hystericus
  • Laryngospasm
  • Vocal cord dysfunction
• Miscellaneous
  • Scombroid fish poisoning
  • Serum sickness
  • Phaeochromocytoma
  • Systemic mastocytosis

Treatment

• Managing a patient with food allergy consists of two important principles:
  • making the patient safe by providing an anaphylaxis plan and educating in its use, and
  • accurately identifying the likely food allergen and educating the patient in allergen avoidance

Immediate Management:

• Address potential life threats
  • Stop trigger
  • Call for help
  • Position supine (head down)
  • O2 (FiO2 1.0 if possible)
  • Exclude alternatives

• Pulse present
  • Adrenaline 0.5mg IM
  • IV access
  • Fluid boluses if SBP <90mmHg – 10-20mL/kg
  • Hydrocortisone – 4 mg/kg IV or IM then 2-4mg q6h
  • Persistant hypotension/bronchospasm -> repeat Adrenaline 0.5mg IM after 5 minutes
  • if still persists after 5 minutes start adrenaline infusion

• Pulse absent
  • CPR
  • Raise legs
  • 2 large IVs
  • 2 L IVF
  • Increasing Adrenaline (adult – 1-4mg) (children – 10-100mcg/kg)
  • Extended CPR

• Persisting hypotension
  • Ranitidine (H2 antagonism)
  • Adrenaline/Noradrenaline infusion
  • Invasive monitoring
  • Colloid

• Persistant bronchospasm
  • As per asthmatic emergencies

• Persisting angioedema
  • Nebulised adrenaline (1mg)
  • ETT
  • Cricothyroidotomy
  • Tracheostomy

Adrenaline 

• Dose:
  • Adults: 500mcg IM
  • Kids: 10 microgram/kg or 0.01 mL/kg of 1:1000 (maximum 0.5 mL)
  • Repeat after 5 minutes if not improving
  • IV adrenaline
    • may be given if there is no resolution despite multiple doses of IM adrenaline 
    • APLS guidelines suggest 0.1-5.0 micrograms/kg/min
      •     grab 1 mg of adrenaline 1:10,000 from the resus trolley
      •     inject into 1000mL bag of normal saline
      •     start infusion at 1 mL/min, which is 1 microgram/min
      •     (this would be 0.1 micrograms/kg/min for a 10 kg child)
      •     increase rate until resolution of severe anaphylaxis
    • Overdose can cause life-threatening tachyarryhthmias or even Tako-tsubo cardiomyopathy
• Patients on beta-blockers
  • who do not respond to adrenaline may benefit from glucagon IV (20 to 30 mcg/kg up to a maximum of 1mg).
• Adrenaline is the first line and most important drug used in an acute allergic reaction.
  • Antihistamines and corticosteroids are second line therapy.
• Adrenaline should be administered IM, not subcutaneously.
  • It should not be administered IV in concentrations of greater than 1:10,000, and then only in dire straits.
• There is no absolute contraindication to the use of adrenaline in patients with heart disease who experience anaphylaxis

If mild-moderate allergic to reaction, administer a non-sedative antihistamine

Cetirizine:

• 1–2 years – 2.5 mg oral
• 2–6 years – 5 mg oral
• 6 years and above – 10 mg oral
• Note: cetirizine has been shown to be safe in infants from  6 months of age (0.25 mg/kg/dose)

Loratadine:

• 1–2 years, oral 2.5 mg once daily
• >2 years and <30 kg, oral 5 mg once daily
• >30 kg, oral 10 mg once daily

Follow up

• Adrenaline Autoinjector – provide prescriptions and ensure that the patient is able to fill them
• ensure that the patient can access to emergency medical services (e.g. phone, not too remote)

• Written Allergy action plan: (Give plan even if food not yet confirmed by investigation)
  • ASCIA anaphylaxis red plan
  • ASCIA allergy green plan

Education

• On strict avoidance of suspected food allergen
• education on reading ingredient labels ( ASCIA Dietary avoidance handouts)
• specific advice for suspected tree-nut allergies:
  • if reacted to walnuts, avoid pecans and vice-versa
  • if reacted to cashews, avoid pistachios and vice-versa
• If there is uncertainty an oral food challenge may be considered. 
• Where multiple foods are to be avoided, dietician referral is recommended
• teach use of adrenaline auto-injector

• optimal control of asthma  – the vast majority of fatalities from food anaphylaxis (75–98%)
  occur in asthmatics, which suggests that optimal asthma control is another important management aim.

• Survival tips for people with food allergy
  • Know your allergy triggers
  • Be educated in careful dietary avoidance
  • Have excellent asthma control
  • Carry injectable adrenaline at all times and be confident in its use
  • Get a ‘buddy’: make sure a friend or relative knows what to do in the event of a reaction
  • When eating out, telephone ahead to notify friends or restaurants of your allergy
  • When eating ‘allergen free’ food you haven’t prepared yourself: ‘touch test’ on the lip before eating

• Consultation with local paediatric/allergy team when
  • To all patients with life threatening allergic features attributed to food exposure
  • Child with suspected allergy and unstable asthma
  • Unclear food trigger or equivocal investigations
  • Multiple food allergies
• Suspected tolerance to food on follow-up and which may require an Oral Food Challenge
• ASCIA Travel Plan Anaphylaxis
• ASCIA PC Checklist Anaphylaxis Travel

Desensitisation therapy/ Allergen immunotherapy 

• Evidence that food allergy can be controlled in this way is very limited, although research is ongoing.
• Most food allergy immunotherapy methods are not currently approved for routine treatment of food allergy globally.
• Current only recommendations are for
  • for the treatment of potentially life threatening allergic reactions to stinging insects.
    • bee
    • wasp
    • Jack Jumper Ant
  • for treatment of allergic rhinitis (hay fever) due to
    • pollen
    • dust mite
      • when:
        • Symptoms are severe.
        • The cause is difficult to avoid, such as grass pollen.
        • Medications don’t help or cause adverse side effects.
        • People prefer to avoid medications