Introduction
An acute allergic reaction or anaphylaxis is a life-threatening but rapidly reversible condition if treated promptly.
Anaphylaxis can develop within minutes of injection or ingestion of medicines or contact with allergen.
Persons who are aware of the risk of anaphylaxis are to be informed of avoidance measures, and may be taught the use of an epinephrine (adrenaline) pen.
Causes of acute allergic reaction or anaphylaxis
- Bee or other insect stings
- Drugs e.g. penicillins, sulphonamides
- Vaccines
- Antisera e.g. snake serum, anti-tetanus serum
- Intravenous contrast media
- Foods like seafood, groundnuts, fruit etc.
Symptoms of acute allergic reaction or anaphylaxis
- Severe itching
- Urticarial rash
- Facial and peri-oral swelling
- Difficulty in breathing
- Wheeze
- Collapse
- Syncope
Signs of acute allergic reaction or anaphylaxis
- Angio-oedema
- Difficulty in breathing
- Bronchospasm with wheeze
- Tachycardia
- Hypotension
- Cold clammy extremities
- Facial oedema
- Urticaria
- Cyanosis
Investigations
- FBC (eosinophilia)
- Skin prick test for specific allergens
- Serum specific IgE
Treatment for acute allergic reaction or anaphylaxis
Objectives
- Secure airways, breathing and circulation
- Reverse symptoms
- Remove the offending cause if possible
- Rapidly intervene and correct abnormal vital signs
Non-pharmacological treatment
- Avoid the allergen
- Resuscitation
Pharmacological treatment
A. Acute Anaphylactic Reaction
1st Line Treatment
Evidence Rating: [B]
Oxygen
By nasal prongs 2-6 L/min
Or
Face mask 4-8 L/min
Or
Non-rebreather mask, 10-15 L/min
And
Adrenaline (Epinephrine), IM,
Adults: 0.3-0.5 ml of 1:1000 solution
(i.e. 300-500 micrograms) repeated if necessary every 10 minutes and while monitoring blood pressure and pulse
Children:
0.3 ml of 1:1000 solution (i.e. 300 micrograms). Repeat as for adults.
And
Hydrocortisone, IV,
Adults:
100-200 mg 6-8 hourly, to control any late allergic reaction that may occur
Children:
All ages; 250 mg/day
Then
Prednisolone, oral,
Adults:
2 mg/kg 6 hourly for 4 doses, not to exceed 40 mg daily for 14 days and taper off
Children
2 mg/kg daily for 14 days and taper off
And
Promethazine hydrochloride, IM,
Adults
25 mg repeat after 2 hours if necessary,
Then 12 hourly for 24 hours
Children
- 2 years-12 years; 6.25-12.5 mg 8-12 hourly for 24 hours
- < 2 years; Not recommended
Or
Chlorpheniramine, IM,
Adults 5-10 mg 6 hourly (max. of 40 mg daily)
Children
- 6-12 years; 5mg up to a max. of 4 doses in 24 hours
- 6 months-6 years; 2.5 mg,
- < 6 month; 250 microgram/kg (max. 1.5 mg)
B. Acute Anaphylactic Reaction with severe airway obstruction)
Above plan
And
Salbutamol, nebulised,
Adults: 5 mg 4-6 hourly until resolved
Children: 2.5 mg 4-6 hourly until resolved
Or
Aminophylline, IV,
Adults:
250 mg over 20 minutes, then continuous infusion by perfusor at 0.5 mg/kg/hour for 24 hours if necessary
Children:
3-5 mg/kg over 20 minutes as a slow bolus injection or by infusion in 500 ml Sodium Chloride 0.9%, IV, 4-6 hourly for 24 hours
C. Acute Anaphylactic Reaction with severe hypotension
Above plan
And
Normal saline, 0.9%, IV, 1 L – 4 L, rate determined by clinical assessment
Referral Criteria
Refer to district or regional hospital if symptoms of anaphylaxis persist after stabilizing the patient and giving initial treatment.