Allergic reactions in a child - anaphylaxis, allergic rhinitis, CMPA, food allergy

Question 1

How does the adrenline dose for anaphylaxis vary in children with known anaphylaxis for self-administration?

Answer 1

Children with known anaphylaxis are issued with self-administration injections containing the correct dose appropriate to body weight

Question 2

What is the 1g in 10,000ml concentration of adrenaline used in ?

Answer 2

Cardiac arrest

Question 3

How much adrenaline should be given in anaphylaxis in different age groups?

Answer 3

<6 yrs - 150mcg

>6 yrs - 300 mcg

NB: the higher dose of 500mcg has been removed from the EpiPen market

Question 4

Define anaphylaxis.

Answer 4

RCPCH

Severe generalised or systemic, life-threatening, hypersensitivity reaction, in which both of the following criteria are met:

1. Sudden onset and rapid progression of symptoms
2. 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.

Question 5

How common is anaphylaxis?

Answer 5

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.

Question 6

What are the most common triggers for anaphylaxis in children?

Answer 6

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.

Question 7

What are the risk factors for fatal outcome in anaphylaxis?

Answer 7

Adolescent age group

Coexistent asthma

Nut allergy

Question 8

What are the risk factors for severe allergic reactions in children?

Answer 8

Question 9

What is the aetiology of anaphylaxis?

Answer 9

Usually IgE-mediated reactions to the allergen

Non-IgE mediated reactions can also occur, most commonly with drugs.

Question 10

What is the pathophysiology/signs and symptoms of anaphylaxis?

Answer 10

Airway narrowing - laryngeal or pharyngeal oedema

Breathing difficulties - bronchospasm with tachypnoea

Cardiovascular compromise - hypotension and/or tachycardia

Mucosal and skin changes

Question 11

What % of anaphylactic reactions do not present with skin signs?

Answer 11

10-20% - this may delay diagnosis

Question 12

What are the ABCDE findings in anaphylaxis?

Answer 12

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)

Question 13

Where should adrenaline be injected during anaphylaxis?

Answer 13

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)

Question 14

What is the management of anaphylaxis after the ABCDE assessment?

Answer 14

1. Call for help
2. Reposition - sit up if breathing difficulties, supine and elevate legs if hypotensive, recovery position if unconscious, BLS/ALS if necessary
3. Adrenaline 1:1000 IM (150mcg <6 years, 300mcg 6-12 years, 500mcg >12 years)
4. 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
5. Admit and monitor for 6-12 hours
   
   • Pulse oximetry
   • ECG
   • BP

Question 15

What is the long-term management of anaphylaxis?

Answer 15

1. Allergen avoidance
2. 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

Question 16

Why is monitoring for at least 6-12 hours important?

Answer 16

Biphasic reactions may occur i.e. the recurrence of symptoms requiring treatment following complete resolution, and usually occur within 6-12 hours

Question 17

What should the initial history include for anaphylaxis?

Answer 17

Exposures immediately prior to the episode of anaphylaxis.]

Question 18

What is the role of mast cell tryptase levels in childre?

Answer 18

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).

Question 19

How are mild/moderate allergic reactions managed?

Answer 19

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)

Question 20

What is the difference between chlorphenamine and citrizine in terms of side-effects?

Answer 20

Chlorpenamine = sedating antihistamine

Cetirizine = non-sedating antihistamine

Question 21

What are the differential diagnoses for anaphylaxis?

Answer 21

• 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

Question 22

What is allergic rhinitis?

Answer 22

Type 1 hypersensitivity reaction to allergens such as hay, pollen, dust, animal hair and mould spores. Causes nasal inflammation.

Question 23

How common is allergic rhinitis?

Answer 23

Affects 1 in 5

80% develop symptoms before age 20

Question 24

What is the aetiology of allergic rhinitis?

Answer 24

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.

Question 25

What are the symptoms of allergic rhinitis?

Answer 25

* **Nasal obstruction, congestion** - related to excess fluid in facial tissues and begins minutes after exposure to allergen. * **Sneezing** * **Red/itchy swollen eyes**

Question 26

What are the problems associated with episodes of allergic rhinitis in children?

Answer 26

Can affect concentration, sleep and work/school attendance.

Question 27

What conditions is allergic rhinitis associated with?

Answer 27

Asthma FH of atopy First born children

Question 28

How is allergic rhinitis diagnosed?

Answer 28

Skin prick test Specific serum IgE levels

Question 29

What is the management of allergic rhinitis?

Answer 29

* Allergen avoidance * Antihistamines e.g. cetirizine * Nasal washes * If severe, desensitisation with gradual slow exposure to allergen (e.g. Grasax for pollen immunotherapy)

Question 30

How is a food intolerance different from food allergy?

Answer 30

**Food intolerance** - non-immunological hypersensitivity reaction to a specific food **Food allergy** - pathological immune response, usually IgE mediated, mounted against a specific food protein.

Question 31

How common is CMPA/CMPI?

Answer 31

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**.

Question 32

What is the aetiology of CMPA/CMPI?

Answer 32

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

Question 33

What should the examination of a child with suspected CMPA involve?

Answer 33

1. Ask about symptoms and relevant timing 2. Examine for nutritional status and comorbid atopy 3. Arrange skin-prick testing and/or serum-specific IgE allergy testing if there is suspected IgE-mediated allergy

Question 34

What are the clinical features of CMPA/CMPI?

Answer 34

* Regurgitation and vomiting * Diarrhoea * Urticaria, atopic eczema * 'Colic' symptoms, irritability, crying * Wheeze, chornic cough ## Footnote ***Rarely angioedema and anaphylaxis may occur.***

Question 35

How is CMPA diagnosed?

Answer 35

* 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

Question 36

What is the management of CMPA?

Answer 36

1. Refer to paediatrician if symptoms are severe (e.g. failure to thrive) 2. Hypoallergenic formula replacement * If mild-moderate symptoms --\> eHF (extensive hydrolysed formula) * If severe CMPA or no response to eHF --\> amino acid-based formula ## Footnote *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.*

Question 37

What is the management of CMPA in exclusively breastfed infants?

Answer 37

1. Continue breastfeeding 2. Eliminate CMP from mother's diet - consider calcium supplements for mother to prevent deficiency during exclusion of cow's milk 3. Use eHF when breastfeeding stops

Question 38

What is the prognosis of CMPA/CMPI? How do you check for tolerance at later stage?

Answer 38

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.

Question 39

Is goat's milk a replacement for cow's milk in CMPA?

Answer 39

No - the proteins contained in both are very similar.

Question 40

Is food allergy usually primary or secondary?

Answer 40

Usually oocurs on primary exposure to the food

Question 41

What are the most common food allergies in infants and older children?

Answer 41

Infants - milk, egg, peanut Older children - peanut, tree nut, fish, shellfish

Question 42

When can food allergies be secondary?

Answer 42

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.* ## Footnote *This is **pollen food allergy syndrome.***

Question 43

What are the symptoms of pollen food allergy syndrome?

Answer 43

Mild such as itchy mouth, but no systemic symptoms.

Question 44

What are the clinical features of IgE mediated food allergy?

Answer 44

Allergic symptoms occurring 10-15 min (\<2 hours) after ingestion of a food e.g. urticaria, facial swelling, anaphylaxis

Question 45

What are the clinical features of non-IgE mediated food allergy?

Answer 45

* Diarrhoea * Abdominal pain * Faltering growth. * Colic * Eczema * Blood in stools in first few weeks of life from proctitis * Severe repetitive vomiting

Question 46

What is a complication of food allergy induced vomiting in infants?

Answer 46

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

Question 47

How are food allergies diagnosed?

Answer 47

* **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 c**linical 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

Question 48

How do you confirm allergy with skin-prick testing?

Answer 48

4mm weal and flare reaction should be produced

Question 49

What is the management of food allergy?

Answer 49

1. Avoidance 2. Refer to dietician for advice about alternative foods and how to avoid nutritional deficiencies 3. Written self-mangement plan and training about anaphylaxis management 4. Non-sedating antihistamines for mild-reactions (without cardiorespiratory symptoms)

Question 50

What is the prognosis with food allergies in childhood?

Answer 50

* 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