Allergic reactions in a child - anaphylaxis, allergic rhinitis, CMPA, food allergy Flashcards
How does the adrenline dose for anaphylaxis vary in children with known anaphylaxis for self-administration?
Children with known anaphylaxis are issued with self-administration injections containing the correct dose appropriate to body weight
What is the 1g in 10,000ml concentration of adrenaline used in ?
Cardiac arrest
How much adrenaline should be given in anaphylaxis in different age groups?
<6 yrs - 150mcg
>6 yrs - 300 mcg
NB: the higher dose of 500mcg has been removed from the EpiPen market
Define anaphylaxis.
RCPCH
Severe generalised or systemic, life-threatening, hypersensitivity reaction, in which both of the following criteria are met:
- Sudden onset and rapid progression of symptoms
- Life-threatening airway and/or breahing and/or circulation problems.
Skin and/or mucosal changes (flushing/urticaria/angioedema) can also occur, but are absent in a significant proportion of cases.
How common is anaphylaxis?
1 episode every 20,000 person years
1 in 1000 cases are fatal
Fatal cases usually in adolescents with a nut allergy but most cases in children <5 years as this is when food allergy is most common.
What are the most common triggers for anaphylaxis in children?
85% of cases due to food
Other allergens include: insect stings, drugs, latex, exercise, inhalant allergens and idiopathic.
NB: in adults the most common trigger is medicinal products.
What are the risk factors for fatal outcome in anaphylaxis?
Adolescent age group
Coexistent asthma
Nut allergy
What are the risk factors for severe allergic reactions in children?
What is the aetiology of anaphylaxis?
Usually IgE-mediated reactions to the allergen
Non-IgE mediated reactions can also occur, most commonly with drugs.
What is the pathophysiology/signs and symptoms of anaphylaxis?
Airway narrowing - laryngeal or pharyngeal oedema
Breathing difficulties - bronchospasm with tachypnoea
Cardiovascular compromise - hypotension and/or tachycardia
Mucosal and skin changes
What % of anaphylactic reactions do not present with skin signs?
10-20% - this may delay diagnosis
What are the ABCDE findings in anaphylaxis?
Airway: swelling, hoarseness, stridor
Breathing: tachypnoea, wheeze, SpO2 <92%,
Circulation: cyanosis, pale, clammy, hypotension,
Disability: drowsy, coma
Exposure: skin can show urticaria, angioedema (not always present)
Where should adrenaline be injected during anaphylaxis?
Anterolateral aspect of the middle third of the thigh
0.15ml or 0.30ml of 1:1000 adrenaline (i.e. 1mg/ml or 1g per 1000ml)
What is the management of anaphylaxis after the ABCDE assessment?
- Call for help
- Reposition - sit up if breathing difficulties, supine and elevate legs if hypotensive, recovery position if unconscious, BLS/ALS if necessary
- Adrenaline 1:1000 IM (150mcg <6 years, 300mcg 6-12 years, 500mcg >12 years)
- Other:
- Establish airway
- High-flow oxygen
- IV fluid challenge (20ml/kg crystalloids in children)
- Chlorpheniramine (IM or slow IV)
- Hydrocortisone (IM or slow IV)
- Consider salbutamol if wheeze
- Admit and monitor for 6-12 hours
- Pulse oximetry
- ECG
- BP
What is the long-term management of anaphylaxis?
- Allergen avoidance
- Adrenaline auto-injector provision and education about use. Two should be prescribed, ensure each is in date.
+/- allergen immunotherapy may be given in cases of insect sting anaphylaxis
Why is monitoring for at least 6-12 hours important?
Biphasic reactions may occur i.e. the recurrence of symptoms requiring treatment following complete resolution, and usually occur within 6-12 hours
What should the initial history include for anaphylaxis?
Exposures immediately prior to the episode of anaphylaxis.]
What is the role of mast cell tryptase levels in childre?
Little evidence for its use in children - in adults it may be indicative of a true episode of anaphylaxis and should be measured immediately after the episode and additionally 1-2 hours after (but not later than 4 hours after anaphylaxis).
How are mild/moderate allergic reactions managed?
Usually at home with oral antihistamines:
Under 2 years of age: Chlorphenamine 1mg (2.5mls)
2 - 6 years of age - Cetirizine 5mg (5mls)
Over 6 years of age - Cetirizine 10mg (10 mls)
What is the difference between chlorphenamine and citrizine in terms of side-effects?
Chlorpenamine = sedating antihistamine
Cetirizine = non-sedating antihistamine
What are the differential diagnoses for anaphylaxis?
- Acute exacerbation of asthma
- Panic attack
- Vocal cord dysfunction
- Generalised acute urticaria
- Non-allergic angioedema
- Systemic mast cell disorders
- Foreign body aspiration
- Acute poisoning
- Hypoglycaemia
- Vasovagal reactions
What is allergic rhinitis?
Type 1 hypersensitivity reaction to allergens such as hay, pollen, dust, animal hair and mould spores. Causes nasal inflammation.
How common is allergic rhinitis?
Affects 1 in 5
80% develop symptoms before age 20
What is the aetiology of allergic rhinitis?
Type 1 hypersensitivity reaction i.e. immediate type, IgE-mediated. IgE is bound to mast cells via its Fc portion. When specific allergen binds to the IgE bound to mast cells, it causes cross-linking and degranulation leading to histamine release.
Usually occurs when the child has not been exposure to the allergen from a young age.
What are the symptoms of allergic rhinitis?
- Nasal obstruction, congestion - related to excess fluid in facial tissues and begins minutes after exposure to allergen.
- Sneezing
- Red/itchy swollen eyes
What are the problems associated with episodes of allergic rhinitis in children?
Can affect concentration, sleep and work/school attendance.
What conditions is allergic rhinitis associated with?
Asthma
FH of atopy
First born children
How is allergic rhinitis diagnosed?
Skin prick test
Specific serum IgE levels
What is the management of allergic rhinitis?
- Allergen avoidance
- Antihistamines e.g. cetirizine
- Nasal washes
- If severe, desensitisation with gradual slow exposure to allergen (e.g. Grasax for pollen immunotherapy)
How is a food intolerance different from food allergy?
Food intolerance - non-immunological hypersensitivity reaction to a specific food
Food allergy - pathological immune response, usually IgE mediated, mounted against a specific food protein.
How common is CMPA/CMPI?
Affects 3-6% of infants and typically occurs in first 3 months of life in formula-fed infants, although rarely seen in exclusively breastfed infants too.
What is the aetiology of CMPA/CMPI?
Immediate (IgE-mediated, <2 hours after ingestion) and delayed (non-IgE mediated, usually 2-72 hours after ingestion) reactions seen.
CMPA = usually immediate
CMPI = mild-moderate delayed reactions
What should the examination of a child with suspected CMPA involve?
- Ask about symptoms and relevant timing
- Examine for nutritional status and comorbid atopy
- Arrange skin-prick testing and/or serum-specific IgE allergy testing if there is suspected IgE-mediated allergy
What are the clinical features of CMPA/CMPI?
- Regurgitation and vomiting
- Diarrhoea
- Urticaria, atopic eczema
- ‘Colic’ symptoms, irritability, crying
- Wheeze, chornic cough
Rarely angioedema and anaphylaxis may occur.
How is CMPA diagnosed?
- Clinically (e.g. improvement with cow’s milk protein elimination)
- Investigations:
- Skin prick/patch testing
- Total IgE and specific IgE (RAST) for cow’s milk protein
What is the management of CMPA?
- Refer to paediatrician if symptoms are severe (e.g. failure to thrive)
- Hypoallergenic formula replacement
- If mild-moderate symptoms –> eHF (extensive hydrolysed formula)
- If severe CMPA or no response to eHF –> amino acid-based formula
NB: around 10% also intolerant to soya, formula replacement should be undertaken for at least 2-4 weeks to see for improvement then continues in mother and infant until child is 9-12 months and for at least 6 months.
What is the management of CMPA in exclusively breastfed infants?
- Continue breastfeeding
- Eliminate CMP from mother’s diet - consider calcium supplements for mother to prevent deficiency during exclusion of cow’s milk
- Use eHF when breastfeeding stops
What is the prognosis of CMPA/CMPI? How do you check for tolerance at later stage?
IgE mediated = around 55% resolves by age 5 years
non-IgE mediated = resolves by age 3 years in most
Oral challenge is undertaken in hospital as anaphylaxis can occur.
Is goat’s milk a replacement for cow’s milk in CMPA?
No - the proteins contained in both are very similar.
Is food allergy usually primary or secondary?
Usually oocurs on primary exposure to the food
What are the most common food allergies in infants and older children?
Infants - milk, egg, peanut
Older children - peanut, tree nut, fish, shellfish
When can food allergies be secondary?
When they are due to cross-reactivity between proteins present in fresh fruits/ vegetables/ nuts and those present in pollens e.g. if a child becomes allergic to birch pollen they may also develop apple allergy because these share a similar protein.
This is pollen food allergy syndrome.
What are the symptoms of pollen food allergy syndrome?
Mild such as itchy mouth, but no systemic symptoms.
What are the clinical features of IgE mediated food allergy?
Allergic symptoms occurring 10-15 min (<2 hours) after ingestion of a food e.g. urticaria, facial swelling, anaphylaxis
What are the clinical features of non-IgE mediated food allergy?
- Diarrhoea
- Abdominal pain
- Faltering growth.
- Colic
- Eczema
- Blood in stools in first few weeks of life from proctitis
- Severe repetitive vomiting
What is a complication of food allergy induced vomiting in infants?
Food protein-induced enterocolitis syndrome (FPIES) - non-IgE mediated (cell-mediated) immune reaction in the GI system to foods, characterized by profuse vomiting and diarrhoea
How are food allergies diagnosed?
- Skin prick tests
- Measurement of specific IgE in blood - false positive results are common but negative skin-prick tests make IgE-mediated allergy unlikely.
- Non-IgE mediated allergies are harder to diagnose and usually based on clinical history and examination. Endoscopy/intestinal biopsy may be used to check for eosinophilic infiltrates to support the diagnosis.
- Food challenge - double-blind placebo-controlled trial of a small amount of the food done in hospital with full resuscitation facilities
How do you confirm allergy with skin-prick testing?
4mm weal and flare reaction should be produced
What is the management of food allergy?
- Avoidance
- Refer to dietician for advice about alternative foods and how to avoid nutritional deficiencies
- Written self-mangement plan and training about anaphylaxis management
- Non-sedating antihistamines for mild-reactions (without cardiorespiratory symptoms)
What is the prognosis with food allergies in childhood?
- Shellfish and nut allergies usually persist through to adulthood
- Egg and cow’s milk protein allergies may resolve in early childhood and can be reintroduced
