Infant allergy

Question 1

What is atopy?

Answer 1

The genetic predisposition for a child to mount an allergic response to common allergens i.e. allergic rhinitis, eczema, asthma, food allergy

Question 2

What are the most common allergens in infants?

Answer 2

• <5 years: milk and eggs

- >5 years: peanuts, tree nuts

Question 3

The 2 main types of allergy

Answer 3

• IgE mediated: acute symptoms most commonly within 20 minutes of exposure: hives, angioedema, analphylaxis
• non-IgE: symptoms within 72 hours of exposure
• can have a mixed presentation too (where clinical history very important)

Question 4

What are food intolerances?

Answer 4

these are not immune-mediated and are more likely to be an enzyme deficiency

Question 5

Signs and symptoms of allergy for IgE and non-IgE (GI, skin, respiratory)

Answer 5

• IgE: nausea, vomiting, diarrhoea, colic, pruritus, erythema, acute urticaria, acute angioedema, anaphylaxis, upper respiratory tract (itchy nose, sneeze), lower respiratory tract (coughing, SOB)
• Non-IgE: reflux, loose stool, constipation, proctocolitis (mucus and blood in stool), reflux, abdominal pain, failure to thrive, significant eczema (early onset <6 months), pruritus, erythema, lower respiratory tract symptoms (SOB, coughing)
• general: lethargy, tiredness, restlessness, distress, poor sleep

Question 6

Diagnosis of allergy

Answer 6

• clinical history: VERY important
• skin prick testing for IgE (using histamine as positive control and saline as negative control)
• IgE specific bloods
• oral food challenge: gold-standard
• non-IgE has no specific diagnostic tool

Question 7

Definition of CMPA, risk factors and prevalence

Answer 7

• allergy to one or more of the 20 proteins in cow’s milk
• risk factors: atopy (current or family history), other allergies
• prevalence: 2-7% in first year of life

Question 8

Guidelines for management of CMPA

Answer 8

• for IgE mediated, need to be treated in hospital with all oral food challenges
• if breast feeding, mother needs to exclude cow’s milk from diet and take 1000mg Ca and 10ug of vitamin D
• for infant, cow’s milk exclusion diet for 2-4 weeks and introduction to confirm diagnosis
• use eHF for children in first instance (unless anaphylaxis, severe eczema or failure to thrive), caesin-based if not weaned (less palatable but more hypoallergenic), whey-based if weaned (more palatable). Can use fortified milk alternatives from 2 years onwards
• amino acid formulas used in severe cases (not very palatable, expensive, but most hypoallergenic)
• after 12 months of cow’s milk exclusion or 6 months from last reaction, in non-IgE can use the milk ladder (with anti-histamines on hand for any accidental exposure), starting with baked goods. If reaction, go down to the last tolerated and stay for 3-6 months then try again

Question 9

Prognosis for CMPA

Answer 9

• IgE 70% tolerate baked goods
• 53-57% IgE outgrow by 5 years, 80% by 16 years
• most non-IgE tolerate milk by 2.5 years

Question 10

The dual allergen hypothesis

Answer 10

• cutaneous exposure: broken skin (i.e. through eczema) exposure to allergens can mount an immune response
• oral food exposure may induce tolerance

Question 11

LEAP study

Answer 11

• Israel has lower levels peanut allergy versus UK due to early exposure (through BAMBA)
• trial looked at giving 6g peanut protein per week from 4 months to ‘at risk’ children
• significantly reduced the risk of developing peanut allergy (70-80%)

Question 12

EAT study and subsequent BSACI guidelines

Answer 12

• looked at early introduction (from 3 months) to general population of: milk, eggs, peanuts, fish, whear, sesame. 2g of each protein twice per week
• only 42% managed to adhere fully
• those that did adhere showed a significant reduction in egg and peanut allergy
• guidelines are now to introduce egg and peanut at 4 months to higher risk allergy children