Allergy Flashcards
What is a food allergy?
A hypersensitivity reaction caused by the immune system becoming abnormally sensitised to stimuli (food proteins)
Describe primary and secondary food allergies
Primary = Child has failed to develop immune tolerance
- Infants > cows milk, egg, peanut
- Children > peanut, fish, shellfish
Secondary = Initially tolerate but become allergic later
- ‘Oral allergy syndrome’ > cross-reactivity between proteins in fruit/nuts and pollen
What are the RFs for food allergy?
- Parental atopy
- Atopic eczema
- Asthma
- Allergic rhinitis
What are common food allergens?
6 major foods:
cow’s milk, egg, peanut, fish, soybean, wheat
What are the S/S of a food allergy?
IgE mediated allergy > occurs immediately (within 2hrs)
- Skin = flush, itch, urticaria, angio-oedema, erythema
- Resp = wheeze/cough, stridor, laryngeal oedema, tightness
- CVS = tachycardia, hypotension
- GI = nausea, D&V, colicky abdominal pain
>Anaphylaxis within 10-15 mins
Non-IgE mediated allergy > delayed (up to 48hrs)
- GI = reflux, dysphagia, blood/mucus in stools, abdominal pain, infantile colic, constipation, food aversion, change in frequency of stools
- Skin = erythema, atopic eczema, pallor
What are the investigations for food allergy?
Allergy focused clinical hx:
- Classify reaction > speed/age of onset, severity, location
- Atopic hx
- Food diary
- Details of food avoidance and why
- Details of feeding hx
Diagnostic tests:
- Skin prick allergy testing
- Measurement of specific IgE antibodies (RAST)
Bloods > signs of inflammation/malabsorption
- Decreased platelets, albumin, iron, haemoglobin
When do you refer a food allergy to a specialist?
- Faltering growth with >=1 GI sx
- Severe atopic eczema
- Multiple allergies
- > =1 acute systemic or severe delayed reactions
- Persisting suspicion
What is the management of food allergy?
Mild reactions (no cardiorespiratory symptoms)
- Non-sedating antihistamines
Education with dietician input
- Avoid relevant foods
- Advice on alternative sources of nutrition / eating out / hidden sources / identifying allergens
- Managing an attack > Allergy Action Plan
- Provide written self-management plans and training
- Information leaflet
> Food allergy to cows’ milk and egg often resolves in early childhood, so gradual reintroduction may be possible
What is allergic rhinitis?
Inflammation of the membrane lining the nose
What is the classification of allergic rhinitis?
Seasonal:
- Sx occur around same time every year
- If occurs secondary to pollen > hay fever
Perennial:
- Sx occur throughout the year
Occupational:
- Sx follow exposure to particular allergens within the workplace
»Intermittent vs persistent / mild vs severe
What are the RFs for allergic rhinitis?
Parental atopy
More likely to occur in first born child (hygiene hypothesis)
What are the S/S of allergic rhinitis?
- Coryza / sneezing
- Conjunctivitis
- Chronic bilateral nasal obstruction
- Post-nasal drip
- Nasal pruritis
- Clear nasal discharge
- Sleep disturbance
- Impaired daytime behaviour / concentration
What are the investigations for allergic rhinitis?
- Identify any co-existent asthma
- Examine nose for nasal polyps, deviated septum, mucosal swelling, depressed / widened nasal bridge
What is the management for allergic rhinitis?
> ALLERGEN AVOIDANCE
Mild/moderate:
- 2-5yrs > oral/liquid antihistamine (cetirizine, loratadine)
- Any age > intranasal azelastine
Moderate/severe:
- Nasal blockage/polyps > intranasal CS (beclomethasone)
- Sneezing/discharge > intranasal CS or oral antihistamine
SCIT (sub-cutaneous immunotherapy):
- Specific allergen immunotherapy
- Used to tx allergic rhinitis, conjunctivitis, insect stings, asthma
- Solutions of an allergic allergen are injected SC on a regular basis for 3-5yrs
What is cows milk protein allergy?
Immune mediated hypersensitivity reaction to cow’s milk protein
When does cows milk protein allergy present?
Typically presents in first 3m of life in formula-fed infants
(rarely in exclusively breast-fed infants)
> COMMON
What type of reaction occurs with cows milk protein allergy?
Both immediate (IgE mediated / CMPA) and delayed (non-IgE mediated / CMPI) reactions are seen
What are RFs for cows milk protein allergy?
- Parental atopy
- Atopic eczema
- Other food allergies
What are the S/S of cows milk protein allergy?
Same as food allergy
- Regurgitation / vomiting, diarrhoea, urticaria, eczema, colic sx, wheeze, chronic cough
- Rarely angioedema and anaphylaxis may occur
What are the investigations for cows milk protein allergy?
Diagnosis often clinical
(e.g. improvement with cow’s milk protein elimination)
- Consider referral for skin prick / patch / RAST testing
What is the management for cows milk protein allergy?
ELIMINATE cow’s milk from diet 2-6w
Breastfed
- Mother to exclude cow’s milk protein from diet
- Consider Ca and vit D supplements
Formula-fed > replace with hypoallergenic infant formula:
- 1st line = extensive hydrolysed formula (eHF)
- 2nd line/severe = Amino acid-based formula (AAF)
Plus:
- Regularly monitor growth
- Nutritional counselling with paediatric dietician
Re-evaluate tolerance every 6-12m:
- Reintroduce
- If tolerance established > greater exposure of less processed milk is advised with ‘Milk Ladder’
